This may seem like odd advice, coming from me, a math professor. Many of the math camps I have seen are geared toward math contest prepping and/or accelerating / remediating in school topics, or geared for gifted kids. I have yet to see a math camp which teaches fun problem solving in a collaborative environment for the regular kid. Maybe they exist, but not here in New Jersey.
Computer camps, Lego mind storms etc are probably better alternatives, as suggested here already. You can also check out the free online Alcumus program on art of problem solving website. That can give you an idea of the type of problems usually found in many math camps.
Try out different interests in the summer to see what clicks. Don’t just limit to STEM topics.