Cornrows make for a low-maintenance summer hairdo
My friend's daughter has extremely unruly naturally curly hair that takes a ton of maintenance to keep from tangling, knotting, etc. They recently went to an amusement park for several days and before she went, she took her daughter to get braids (cornrows) in her hair. She went to the beauty school so it was reasonably priced. Cornrows are easy to maintain while they are on vacation, and tangles won't be an issue on the rides.
I have a friend who gets cornrows every summer. She has long, thick, red hair, and she insists it's the easiest hairstyle to maintain while camping and traveling. If you try this, be sure to sunscreen the exposed areas of your child's scalp -- it will be vulnerable to sunburn.
wikiHow has a good article on the basics of cornrows.