I feel trapped by agreeing to look after my grandchildren

Agree with this!

Do what suits you OP. Their kids, not yours. Their problem to solve. What would they do if you had an accident tomorrow and had a broken leg for a few months? They'd have to sort out an alternative then, so they can sort out an alternative when you are well, too.

My heart really goes out to you, you sound like a wonderful Grandmother. They are taking advantage of you big time! You need to learn the power of the word No. It’s your life and you don’t want to have any regrets looking back and realising you didn’t get to see your other grandchildren as much as you wanted- I’m sure they miss you too. You really need to set some firm boundaries and not let them walk all over you. Threatening to not let you see the children if you don’t comply with their every wish is beyond mean, and cruel to both you and the kids! I urge you to put some boundaries in place. I’ve not read it yet but the self help book ‘Let Them’ by Mel Robbins might be a good one for you to read.

YADNBU. My mum looked after my son once, for an hour, so I could keep an important appointment at the bank. It was the only time I ever asked her for help with childcare. I understood she had her own life to lead and did not like children very much.
My ds3 has had to move back in with me after his relationship broke down. He has four children who are here at least three days each week; I have a life-limiting incurable illness and the stress of 'all this' at my age is deeply upsetting. I know I have set myself on fire to keep them all warm.
You have gone above and beyond with the amount of care you have provided, OP. Please hold firm and don't let your daughters bully you further.

I mind my grandchildren. If I want a long weekend, I simply tell my son that I’m going to book a few days away, can you pick a time that suits. He or his wife simply takes the time off and covers the time themselves. If it’s a longer holiday, I pick a month and they tell me what works, then himself and his wife sort it out.
It wouldn’t work if I felt I didn’t have some control over the situation. You need to be firmer with your daughters, after all, you are saving them money and doing them massive favours.

You look after 5 young kids at once? You must be exhausted! A woman half your age would be! I’d say it’s not about your son but that you want more time for you as you’re exhausted. And let their step mum watch them on the other days as you’re being emotionally blackmailed - I assume they at least cover your costs for food etc? Otherwise you’re effectively paying them in order to help them out!
Dont ask - just say. And if they kick off, ask what they’d do if you got unwell or worse? Tell them you’ve been to your GP and they’ve said your BP is up or something and you need more time to relax. So the max you can do is 3 days a week.

Your daughters are being completely unreasonable and using emotional blackmail to boot!

You are saving them thousands (even cutting it down) and rather than listening to you and respecting your decision they ganged up on you.

Your retirement is for you to enjoy not have a new job which isn't paid 5 days a week!

Agree with other posters tell them don't ask. If you find it too tough in person then send them a message. It's too much and you need time for you as well therefore from x date it will be x number of days set to Tues wed Thurs etc.

What suits you OP? Inform them. Tell don't ask. Give them notice. Set clear boundaries. They are being unreasonable, but you have also enabled it by being a doormat. Set an example to your daughters, show them what dignity and self-respect looks like, alongside an appropriate level of care and support. 2 days a week is generous, really. Far more help than anyone I know has ever received from grandparents. Start living your life in your terms.

What a kind and generous grandparent you are but this generosity is being totally abused. You need to let them know the current arrangement no longer works for you and let them know what your availability will be from next month.
Please plan more time with your son and his family as he sounds more like you - much more pleasant to be around. Stand firm!

I’d be inclined to say ‘I think asking your dad and his wife to chip in with help is a really good idea.’

You seem to be providing childcare 5 days a week and you’re already paying for some fees and/or offering to cover some fees if you do less? Is that right? They really are deeply unreasonable.

Whether or not they like their brother is neither here or there. You’re perfectly entitled to want to spend more time with his children and you don’t need to explain or justify it.

it sounds to me that they have become used to the extra flexibility that your childcare provides - not just fees but not having to be there at a certain pick up time. That might explain their unreasonableness.

They aren’t being fair to you at all.

I think I’d say ‘no more’ or ‘these are the days and times I can do, work it out between yourselves,’ maybe Tuesday-Thursday. Then you have 4 days a week to yourself to spend where and how you like. At the very least, if they were fighting each other for your time/free childcare, they wouldn’t be ganging up on you!

Stop letting them bully you. They 100% won't cut contact. They need you, you're holding the cards here.

Your daughters sound vile OP. What a great example they are setting to those poor kids.
I would never blackmail my mum or MIL like this. Both help out but I have always said I don't expect them to put their lives on hold for us and we also use paid childcare. The grannies cover illness and do an afternoon each but they are not unpaid skivvies.

Your daughters are bullying you. Set out what’s reasonable - I’d suggest Tues evening to Thurs to allow you to go to London on a Friday to Tuesday whenever you want. And half of holidays so can go to London the rest of the time. Let’s your ex husbands new wife do the rest.

Your daughters are extremely selfish and putting your son to one side, expecting you to care for all grandchildren 5 days per week then treating you with no contact is disgraceful. They should be ashamed of themselves. You need to put boundaries in for your sake as you are entitled to you time to see friends, hobbies etc. I wish you well and I would be saying you won’t be supporting them when they cannot treat you with respect.

Goodness, your daughters are outrageous! What a pair of bitches to manipulate you with threats of sending the children to your exh and his wife. That’s bound to hit a nerve.

Five days a week plus some time at the weekend plus holidays with is massively taking advantage of you. On the whole grandparents do a day or two not every bloody day.

Tell them, don’t ask. Set your boundaries. There’s no way their step mother is interested in taking over this schedule, no way. Tell them you will do two or three days, no more weekends, no more holidays.

My mum initially agreed to do childcare for me too, it really didn’t take long before it was apparent that it’s bloody hard work for her. In the end I decided to put DC into childcare because I didn’t want to burden her.

Surely your own children can see or know how hard it must be

They are emotionally manipulating you. Saying they will ask their dads wife instead is just to try and make you feel jealous. I agree with posters who say to call their bluff. I highly doubt she will want to do this every day.
Likewise with saying the children will be devastated. They are just trying to guilt trip you. I think you need to be firm and set out clear expectations. Think about what you are happy to do, and if they don't like it then tough luck.
I assume they are working when you have the children and aren't just using the time to themselves?

Can you be my mum.

She sees my daughter 2 hours once a month and the last time i said how my 3 year old wanted to show her riding her pedal bike in the garden and she said 'no I'm happy chilling here'.

In the end i took my daughter to the park while my mum sat in the house.

In my experience the more you do for selfish people, the more they expect.

Sorry but your daughters sound awful. I could never imagine telling my mum she couldn't see my kids if she didn't do what I wanted.
I would call their bluff and tell them both you can only do 3 days every week as you would like to see your friends and your son.
As a pp said I can't see the step mum wanting to be tied to every day.
Forgot about the money you already help with. How dare they treat you with such disrespect.

Your daughters are mums and need to stop acting like entitled brats.

You’re doing too much for them to the detriment of having the same amount of time with your son and his children. They’re trying to push him out of your life and that’s not for them to decide.

You’re their mum and you have to stand up to them. They sound like horribly manipulative people. Tell them your rules and let them go to their step-mum. It may hurt you inside, but you can’t be manipulated by them either.

I'd probably respond to veiled threats about their new stepmother "taking over" with an enthusiastic "That's great! How very kind of her! It really solves everyone's problem!"

You sound lovely- so incredibly generous towards your children with both your time and money. YANBU in the slightest, completely fair and understandable you’d also like to visit your son and those grandchildren. And even have some time to relax, meet a friend for coffee or pursue a new hobby for you! 💐

"I have a really hard time standing up to my daughters as they often threaten to just cut my contact with my grandchildren who I adore, in favour of their father and his new wife."

I'd take the risk in your place, @OP .

Spot on!
Take this advice OP. It's 🎯

I asked my daughters again today to consider using wraparound care even once or twice a week just to free up more time for weekend visits and to consider holiday clubs again

You ASKED them? That was a mistake. You should have told them you were cutting down to 3 days in X amount of weeks/months in order to have a bit of a life and you were just giving them plenty of time to make alternative arrangements. They sound hideous.