Start with checking the laws in your area, and your insurance coverage.
Seriously. This sort of stuff (even day camp) is regulated, and your carrier might have something to say about children potentially being exposed to snakes, poisonous berries on hikes, or falls and diving around pools.
Even if this is all perfectly legal (and check; don't just assume, ferchrissakes), your insurance company will potentially disclaim coverage if a child is injured on your watch and they didn't know you were going to do this. Yes, even if you are running a day care and are experienced, even if the day care is insured. These are different circumstances.
I know these were not the questions you asked, but all it takes is one kid diving into a shallow pool and you could lose your house.