Although I’ve never had an issue with campers giving me tips, I can definitely imagine that there are kids who would use it to tease counselors.
As a parent, I usually give the tips to my children to give, often accompanied by a thank you note from them as well as one from us. I never even thought about the possibility of them misusing the opportunity; they are usually excited to hand it to the counselors, and they feel trustworthy and responsible to be transporting the money. You have to know the individual child.
In the spirit of the Montessori educational method, tipping is one of those “teachable moments,” if we so desire.