Beaches near Tree Limin Extreme

[TEGL]

We are looking into doing the zipline tour with Tree Limin Extreme but its only 3 hours so I am throwing around the idea of hitting up a beach after and just and relaxing.  Are there any beaches near this facility that are recommended?  We will be traveling with our 6yo son who LOVES water sports so if there are any beaches that have these in the water that would be ideal.  
For those of you that have been to St. Thomas because and have other recommendations of things we could do after the zip lining I'd love to hear them.  My little one isn't much into informational/sightseeing tours so those are out!  We have been to St. Thomas twice but its been over 10 years and I am at a loss of what to do that will keep him busy and having fun.  

[Ms411]

Magens is the closest beach but you need to take a taxi. Magens has pedal boats, kayaks, paddleboards. Usually calm water. Sandy bottom.