How much are you agreeing to pay them? If you're struggling to meet general living costs you're probably offering them too much.
I know it's hard! It feels like it's taking the piss to offer something like £20 a month when it's on a huge debt! But if you contact one of the charities, they'll do exactly that (not £20 specifically, but whatever you can afford).
If you'd rather contact them yourself, then how about you do what the charity does? Go through all your essential bills, work out what you need to pay to live - I think you mentioned the Step Change budget so maybe you have a list of what to include but let me know if not.
So, you start by working out what your family needs. Then you see what's left. You target any credit with massive interest (pay day loans perhaps?) or which may cause serious problems (e.g. if you owe tax to the Inland Revenue) and see if you can pay that off first if possible. (I had a bit of cash to do this, not sure what they advise if you don't - possibly best to ask them).
Then all the rest - credit cards, loans etc - they get what's left. If that's £1 each, then so be it. (You may need Step Change or similar to argue this for you - I'd find it hard!) Or it may be you can afford to give them all - say - £30 each. If so then that's all you offer them, no matter what the payment was before - because that's all you have.