My family has always loved camping, I agree with the others there are lots of things they can just naturally find to do, and I loved the pine cone idea, as well as the flowers...
You could also bring things like splash balls, and a tub you can put water in for your daughter to play in - then when she gets older you can camp next to mellow streams to play in. (well she can now too, but its an extra thing to watch out for when they are little) You can also bring some corn starch, its extremely fun for the kids to play with but way too messy at home. You add a small amount of water to corn starch and watch how if you keep it moving it stays somewhat solid then as you stop moving it it turns to a liquid type texture again. A fun science experiment type activity. We also keep a camping log, a notebook in the camper that we can write down our trip highlights in and the kids add pictures or short stories about there favorite parts of the trip.
Have Fun,
S.