The trend towards tipping everyone, everywhere is one of my pet peeves. Waitstaff are payed beneath minimum wage, counter help is not. Now I'll grant you that minimum wage is inadequate, but the difference between waitstaff minimum and other minimum wages is to account for the fact that tipping of waitstaff is expected.
Daycamp has an alternate minimum wage in some places too, and it might be worth checking out whether or not staff are being paid at camp minimum or at a level more commensurate with other jobs. Either way, I think that tipping of camp staff, teachers, etc... is a highly questionable practice. At our camp (I worked as a counselor 6 yrs, and as assistant director/director for a combination of seven yrs.) tipping was absolutely prohibited. Our belief was that there should be no appearance of anyone buying special treatment/favoritism for their children via tipping. Camp is expensive enough to begin with--especially if you are sending multiple kids. To add a pressure to tip on top of that is (I think) disrespectful to families.
I don't think it is inappropriate to give a thank you gift, but I think such gifts should be small (a $5 coffee card or bookstore certificate; a container with sticky notes and pretty paper clips for a teacher; etc.) and definitely not mandatory. And I have to say that as a teacher, I agree with Master of None--a letter to a supervisor is a far more meaningful to me than a gift card or cash. I always know it is a genuine, vs. pro forma kind gesture.
