To issue ultimatum to DH about his ex?

Yanbu op. No way would i put up with this

Why is everyone trying to fit the children into her shift patterns? The children’s needs should come first, and changing days randomly plus not knowing where they’re sleeping from day to day is going to cause them much anxiety. It needs to stop and regular days with each parent needs to happen.
OP, your DH needs to go to court for a Child arrangement order - he should have a set routine in place and she should fit her shifts in around the days she doesn’t have her children, or arrange paid for childcare.

Maybe he does. But he’s expecting op to facilitate that, which is not ok. Op also gets a say seeing as she’s being used as the child care, doing a lot of the donkey work by collecting the kids, preparing meals and taking the to activities last minute.

It's not about "she eon't stop him seeing the kids", she absolutely can't stop him, it is not up to her. They have 50/50 custody, which is the norm in the UK and the court's strong preference.

Get a more formal custody arrangement, if needs be, and build in rules and boundaries (e.g. either fixed days, which she will have to manage with childcare on her days) or a flexible approach but finalised at the start of every week.

She can't reduce contact with the kids just because she decides to, the law doesn't work like that, and your husband has equal rights.

You don’t need to issue an ultimatum. Just stop helping. At all. He doesn’t need to set a boundary with his ex, because you do everything. If you want the situation to change all you have to do is let him deal with the consequences of his actions. Walk into the house, put your pjs on, make yourself something to eat and go and watch tv. Let him work out to get the kids home after an activity. If you don’t think you can just sit there and watch him struggle, stay out late and turn your phone off.

Could both parents have the children a week at a time, ie one week on and then one week?

That would stop this happening!

You don’t always have to say yes. I didn’t when I worked in the NHS. I agreed if it suited me but if it didn’t I refused.

If he wants an easy life he will need you to be on board with all this. So, do it, give him an ultimatum. He will be much worse off if you aren't there to pick up his slack. And as someone else said, she's not going to stop contact. She can't afford to.

I bet she doesn't give the precise shifts as she is probably using you for free babysitting half the time. If she tells you her shifts then she can't add extra days here and there.

I'd move out.

The poor DC. The situation is appalling for them. That’s reason enough to call time on it so please do.

It wasnt in the OP, but she later says that she also works in the NHS so knows that shift rotas are released much earlier than the day before. DD is NHS and gets her off rota weeks in advance.

It isn't selfish. I would not wish step parenting on anyone. I refused to date anyone with children or an ex wife in the picture. Is just asking for problems.

The OP said the ex works in the NHS now and she herself has stressful shift job, didn't mention NHS.
I too would step back and say no a few times see if he will actually step up and get things sorted.
When I was in the NHS we had our rota 6 weeks at a time.

Well, if you can't get DH to change his behavior, you change yours. Schedule your life around your life. Let DH sort out his issues with his ex and kid care. Remove yourself from his scheduling nightmare.

Why do you think she is doing all of this so last minute OP? Is it genuine bad planning or is she trying to make life hard for you? Either way it isn’t ok, it’s just very odd behaviour.

Whilst I agree that the children shouldnt suffer, the only reason that they arent is because @PicassoDiBablo is doing what neither of the parents are doing.

If there is one person here (apart from the kids) who has no actual parenting responsibility to the SC, its the OP. So why the hell is she being expected to do it when all it would take is both parents actually stepping up and doing it themselves?! Because so far, she has. She has sleepwalked into being a free emergency nanny and in the process, her own child is suffering just as much upheaval and lack of security as the SC are. I would argue that the OP putting her foot down and saying "NO MORE" and forcing the parents to deal with it is in fact doing the kids a massive favour as they will have more security going forward than they currently have.

As the saying goes "A lack of planning on your part does not constitute an emergency on mine".

This isn't an issue of last-minute shift changes it seems but a complete absence of information from your DH's ex. It would be one thing if she sent you the rota but had to deal with last minute changes or cover - she's not giving you any info and that's a deliberate, shitty choice. She's being a crap parent by messing her DC around and frankly your DH is being a crap parent by letting her. He's also being a crap partner. You're completely in the right to demand change and set boundaries.

There’s some awfully cold responses on here, this one included where the children involved are shown so little compassion 😕 OP has been in their lives a parent figure for years now, it’s awful to think they should be disregarded.
this is between the adults and need to stay that way.
OP needs her DH to get legal advice about where he stands with all of this and move forward that way I’d say and absolutely nobody in this scenario has currently taken responsibility for the situation.

This would drive me insane, I don't blame you for being cross.

Not your circus, not your monkeys.

Tell your DH he needs to speak to his EX about planning ahead, otherwise you're not prepared to rush around filling in for people so disorganised.

You should take a step back from all this, and let them figure themselves out, since nobody is currently listening to you, yet they're falling back on you when they need your help.

I’d do the live somewhere else for a couple of weeks. He can only do this because you facilitate, so stop. Tell him to tell her he will need x days notice or he will go to court to set his access more rigidly / have full access and she can have them when suits.

For at least the last 12 months my ward has been so understaffed due to actual understaffing and then extra understaffing due to long term sickness caused by the extra pressure of the understaffing; I've been called in almost every week on my days off or asked to work double shifts etc.

Can you stay somewhere else for a while to force him to deal with it all on his own?

This

So things worked well between you re the SDCs until she started working? It sounds like she's deliberately yanking you around - unless she is genuinely the most disorganised person ever - has something happened in the past couple of years that would make her behave like this, a falling out with your DH for example? Otherwise it's baffling behaviour. Hope you can get it sorted out.