My advice is to send children to our relatives houses, villages, or we can arrange for some tour and take children to many places. As the children are facing stressful life in schools, they will longing to go out to enjoy. Ofcourse summer camps teaches some useful things like swimming etc.., but children will be again engaged as regular timings even in their holidays. Leave the kids free, give them healthy foods, take them out, make them feel happy. Their vision will improve, they will ask more questions when taken out to new places.
Let the children enjoy their best atleast in holidays.