Have you already exhausted all your summer ideas one month into the summer? Are your kids bored? Is your house trashed? May I present one solution? The summer job chart. Each job they perform is worth one space around here -- clean bathroom sink = 1; clean toilet = 1; unload/reload dishwasher = 1; make bed =1. You get the idea. For younger children, you may want to give them two points per job or they might never finish.
I just took pieces of poster board and drew a little path and then sectioned it off. The kids helped me color and stamp it. About every 20 to 25 spaces there is a reward -- ice cream at McDonald's, a slurpee, a trip to the dollar store, a book at Half-Price Books, et cetera. The prizes get more expensive near the end ($10 at store of their choice) culminating in a summer movie of their choice. I made a marker for each child using some Stampin' Up stamps I have, colored them in and then "laminated" them with packaging tape. I use masking tape on the back, but you could easily magnetize them and put the game on the refrigerator. I'm thinking mine might go there next year.
My kids ask me for work, and I already got all of my downstairs blinds cleaned on the first day I put it up (which was just last week -- a little late this year). I made this chart a couple of summers ago and have saved it to reuse. I don't use it every summer, because the kids get bored of it. I alternate it with other things, but we're back to it this year. So go make your own game so your kids will stop complaining that they're bored and will start cleaning your house. :)