I think camping outside is totally normal and part of growing up. Did this so many times as a kid with my cousins or sleeping on the trampoline as others have said.
Perhaps keep Facebook posts about it till afterwards or not at all if u are that worried. But the actual camping I think is great and fun for the kids and gives them a sense of independence. I think it would be mean to not allow this and install a sense of fear into them. Use your judgement as to what age u think they are prepared for it tho. And maybe try camping with them the first time.