I was a camp counselor for seven summers, and I learned one major thing: except for certain special camp events, you really do not need to wear makeup at all. In fact, makeup is liable to look a little pretentious when you’re swimming and playing sports. It’s also really bad for your skin because it just clogs everything up while you’re perspiring in the summer heat.
My suggestion is to take along no more than a bare minimum of makeup (concealer, powder, mascara, blush/bronzer, lip gloss) and use it only for special camp events. My camp would put together a performance each year. Each bunk would prepare a song or two to perform for the parents, and it became a huge thing with costumes and lighting. We counselors were asked to clean up and wear clean, nice clothes and look good for the performance because we might meet the parents. I always wore a little makeup for that.
Having said all of that, your mascara should be waterproof because you never know what the weather will be during those special events. Mary Kay makes a wonderful waterproof mascara.
What you absolutely should do is focus on skin care. Bring along a gentle face cleanser, non-comedogenic moisturizer with SPF, and lip balm with SPF, as well as any special things like acne treatments. And don’t forget regular sunscreen for face and body with SPF 30 or higher.