I'm not sure how many summer holidays you have on your side of the pond, or if you're meaning the entire summer (what we call "summer vacation" for the kids when they're home from school).
For me, the main three are Memorial Day (the unofficial start of summer), the 4th of July, and Labor Day (the unofficial end of summer). Usually, the food called for is the same for all three. Grilled burgers, hot dogs, steaks, Smoked meats, lots of BBQ sauce, corn on the cob, ice cream (homemade is best), potato salad, coleslaw.
As far as camping and cooking outdoors, you might want to go down to the outdoor cooking forums. There's a camp cooking sub-board, as well as Dutch oven, Grill, and Smoking (BBQ).
From personal experience, it's always good to know how to do things "in the rough". I found that out back in December when the ice storm hit my part of the world, and we were without electricity for NINE days. Man, that was rough! Luckily, I have a big grill, and was able to borrow a cassette burner from work. I'd like to get a camp stove, and maybe a Dutch oven or two.
Peace, Love, and Vegetable Rights!
Eat Meat and Save the Plants!