Thanks for all the suggestions.
Tanaqui - I think i will get them to choose their activity and do like you suggest if they spoil another day then theirs doesn't happen.
Candlelight- we have a nature reserve about a 25 minute walk away (at normal pace) with my 5yro walking it can be a little longer - but I suppose it doesn't stop them going ahead with their dad. There us often activities on in the summer and there's 2 different playgrounds and we usually have lunch/ tea at the nearby pub. However typical pre teens hate walking there want us to drive!!! But it's one thing I insist on is walking especially on a nice day . Obviously due to an ages of my 2 they will quite happily sit and play with arts and craft stuff elder 2 it's more computer games etc. But I think we will try swimming more. I'm not a massive fan of swimming but it's fairly in expensive and something we can all do. We have lots of pools near us.
Coco - you would not believe the furore that happens if we do something without them. We been recently to a retail park to pick up a reserved item. Not on theìr day, they detest shopping (My eldest at school) just had youngest with us. We had a family day out apparently ???
Last time it was a week day during term time not on a day we'd have them. I plan every thing from food shopping, haircuts, appts such as dentist etc all around the days they are with us but she had a right whopper about it. Said she is protecting SC so they are not left out, thing is she tells anybody everything, kids hear, and then repeat it all to DH. Although he basically told her to fuck off and we are allowed to go out for the day without them. And yes she actually believes we should only do things as a 6.
Swing- it's 3 days each week. And in the second week I'm at work 2 of the days so DH will have them all, it's not ideal but I couldn't afford all the extra time off. DH will also work round the time he doesn't have them. Tend to stick to similar pattern in the summer.
Time to- I think I will look out for vouchers and discounts and maybe look at half and half, attraction food is ridiculously expensive for what it is but maybe once or twice we could do it.
Blackandwhite- Thank you for your words, I know they are at that age and I do know they are a nightmare for their mum too. It's just disheartening when you feel like you have put a lot if time and effort in and it doesn't feel appreciated. I never give a reaction, I just say we do things different as to when they go out with their mum. They always eat... so it can't be that bad I suppose. There's no problems with the relationships between us or children they love playing with each other. DH and I have talked about it and think it's just managing their expectations mum has 2 to fund, we have 4, and it costs more and we can't always do as a 6 what they can as a 3 (I say 3, mum has a partner so sometimes it is 4) DH does take them quite often to a park near us where they can play football too and the younger ones don't tend to go so he does do things with just the 2 of them.