there is also a Jeep Safari tour in Grand Cayman that goes to Rum Point, and there is a wave runner tour that we loved, it visits stingray city and rum point area. You get two hours on wave runner so it is a blast!!!
In Coz I would recommend ATV's or Helmet diving which is pretty cool so is discover diving if your sons like snorkeling, its the next step. We used Cozumel Cruise Excursion, and they were excellent.