Hi Mimi:
I'm the family cruise editor here. I too am interested in finding out the ages of your children which would help in my recommendations.
We sailed Royal Caribbean many years ago (my daughter was about four then) on a San Juan itinerary and there were plenty of kids on board. This should also be the case when you sail since March and April are popular months due to the varied spring break schedules throughout the country. If you wants tons of kids, then go on the Explorer of the Seas. (I prefer the southern itineraries myself.) We went on Explorer's sister ship, Adventure, and we loved it. My 9 year old daughter has been on 13 cruises and yet she still says the Adventure was the best ever. She loved the rock climbing wall and ice skating show, but even more, she had the best time in the youth program. The counselors were lots of fun and offered a very active program. We had to twist her arm to hang out with us! By the way, by the end of the year, all Royal CAribbean ships will have a rock climbing wall installed on them.
Let me know if you have more questions!
Smooth sailing,
Luisa Frey Gaynor