There is a large poker tournament held every year at the Radisson in September. This year, it maybe late September, but I would check with Amy from MCM Tours to see if that will overlap with your dates. If they do, then maybe consider October or November for your trip.
For a snorkel excursion we loved the Tanquilo http://www.tranquiloaruba.com/ South Side Lunch snorkel cruise. I wrote about our experience here. Otherwise, the concierges at the Radisson can make arrangements for you with any of the other larger operators. De Palm, Red Sail and Pelican all have daily cruises.
All varieties of watersports, including waverunners, are available through any of the watersports operators along Palm Beach. The waverunners do not run along Palm Beach, they are located just a short boat ride away. The watersports operators will handle getting you over there.