I mean really, it is HOT out! So why not enjoy Charleston from the water! Here are some great resources for some Kayaking, Stand Up Paddle boarding and more. These activities are fun for all ages! Check out some of the great companies around town!
The Village Connection :: Old Village Real Estate :: Mount Pleasant, SC 
We did this last weekend when family visited. We had a wide range of ages, and everyone participated! It is a great activity.