Do you have a lone parent group near you? We have no gingerbread near us and I asked my health visitor etc but there wasn't anything. But then i recently found a new lone parent group in my area and it's been brilliant. I has also grown like mad in the few months since it set up last summer.
They have organsied a week away at Easter for all the members, staying at Pontins, couple of day trips to theme park and cinema. Originally they talked about sharing with another family so we could cut the costs and it's be around £75 for the week, but our fab leader managed to get a grant and so all the accomodation is going to be paid for and we will get our own challet!
It's really worth looking for a lone parent group in your area. And if there isn't one how about getting together a few friends and setting one up? We meet monthly at the local indoor play centre and have regular events, some for everyone (cinema trip), some for just the adults (meal out), some for just the dad's (bowling) or mum's (pamper night).
If you can't find anything like that then i would suggest mangokids as someone else said, not tried it myself but have heard good things about it.
Otherwise Pontins or Butlins with others. It can be difficult meeting other adults when you are on your own, so I can understand why you want to find a lone parent holiday. Alos i've done Centre Parcs and it was fab for my son and i enjoyed it too, but i couldn't find anyone to share a villa with so found it worked out quite expensive with just 2 of us in a 4 bed villa. If my sister had been more understanding and not wanted to 'spend time as a family when we go on holiday' ie meaning just her and her husband with their kids then it would be easier for me. Hopefully you'll have more understanding family!
Hope you have a fab time wherever you go
Gilly