Pumpkins and squash sound like a plan, sow indoors before easter holiday in biggish pots, you would need to arrange for someone to keepo an eye on the watering over easter but that is about a half hour once a week if you use a decent sized pot. Sort out some piles of manure and plant out end of May, you should have flowers before summer term breaks up so do the hand pollination thing and let them get on with it. Useful if someone can keep an eye on them through the summer but once again we're lookung at half an hour a week....
Beans for dried beans (grow your own baked beans?) might also work as long as they have a well prepared trench they'll survive without watering.... something like borlotti or yin-yang... same thing really, for the timescale
chrisc
