If you can put up with a bus mans holiday- (i.e. more kids!0, i would recommend you check out your local council- most have council run summer holiday kinds schemes.
I did it a few years back, and the money was much better than retail or catering paid, plus its usually only monday to friday in the day, meaning you still get a life, and if its nice weather you get to do fun stuff outdoors with the kids.
As a former teacher myself, i can tell you my local council were biting my arm off to get me- experience with kids, plus already criminal rcord checked!
You migh even get offered the lead role, which is more money than just the assistants.
Good luck!