When DC were that age we didn't eat out regularly. Cake in a cafe every couple of months. Unfortunately, even without debt it wasn't a huge priority. I couldn't bear the wasted food. If money is tight, which it must be if you have debt, then you need to cut your cloth accordingly.
You could have days out to National Trust places, maybe with friends. They usually have seats and tables for a picnic and space to run around while you finish off. During the school holidays they often set up free trails for children to follow. Some have farms, mazes, adventure playgrounds etc. We would rarely go into the house or mill but they used to have dressing up gear and activities to do.
After the initial outlay if you take a picnic the only cost is the petrol.
In Central Manchester the Science Museum and Manchester Museum are free and have picnic areas and I'm sure that's not unique. Lots of museums are.
Taking a bus or a train somewhere can be an adventure. We got a train to a forest for a walk and picnic which DC loved. Pre strikes obviously.
A beach day can cost very little other than petrol.
Do cinemas still do early morning cheap screenings? Buy your own sweets and drinks beforehand.
Do a bit of research for free and cheap places. There will be lots near where you live.
And finally I bought a book called I'm Bored by Suzy Bennett which had lots of ideas for things to do at home. At least half of the week we didn't go anywhere at all.