beaches in Grand Cayman and Ocho Rios

I am taking 6 teen agers on a Spring Break cruise and want to take them to nice beaches in Grand Cayman and Ocho Rios. The hotels at the 7 mile beach in Cayman won't let you use their facilities unless you are staying at the hotels. Does anyone know where we can go on these 2 islands to spend the day at the beach and also have access to jet skis, parasailing, etc. and food.

I'm the family cruise editor here. Actually we've been to Seven Mile Beach on two different cruises and had no problem using the beach facilities for the day. While I don't remember which beach club areas we swam at, you can ask the shore excursions staff of your cruise ship. Also, the cab drivers known which beaches accept day visitors. You will have to pay a few dollars per person to use the beach chairs, etc. There are plenty of watersports rentals along the beach which should keep your crew of teens busy!
In Jamaica, I strongly suggest going on a shore excursion sold through the cruise line. While I'm usually a big advocate of going out on your own to explore, I think you'd be better off in Jamaica to choose a group tour. Jamaicans are friendly but sometimes too friendly and you may feel intimidated on your own to buy their goods, etc. Dunns River Falls is a big favorite -- you climb the waterfalls as a group.
I hope this helps.
Smooth sailing,
Luisa Frey GAynor