Welcome back, JanaLee! While I haven't experienced the Screamin' Eagle Jet Boats in St. Thomas and St. John, they are very similar to the Twister in the Passion Island by Twister adventure in Cozumel. My friend from Disney Cruise Line was able to tell me all about her experience when we sailed together earlier this year.
The boat is very fast and does quite a few donuts, so be prepared for a wild ride! On her tour, there were kids as young as eight and adults into their seventies all having the time of their lives. She does caution that guests on these boats should prepare to be wet, and by wet, I mean drenched, so wear your swimsuit under a coverup, and if you plan to take photos, be sure it's a waterproof camera. There should be a waterproof locker onboard the boat to store your small bag with personal items. You'll be in for a fun ride!
In St. Maarten, your best bet with your group would be the
French Riviera Beach Rendezvous. For all ages, this adventure takes you on a short air conditioned bus ride to the gorgeous Orient Bay, known as the French Riviera of the Caribbean. With playtime in the sand for young ones, water sports available at an additional fee for the adventure seekers, and of course time to do nothing but soak in the sun and relax, this is the perfect adventure for your entire group. Lunch and drinks are included as well.
Keep me updated as you continue to plan, JanaLee! Your big group is going to have such a magical trip!