YOu may also want to check out some Carnival cruises to the southern Caribbean. Only main problem with the southern itinary is the airfare to San Juan, but you may be able to find that on your own cheaper. We also have our monthly cruise bazaar the first Monday of the month and there will be on tomorrow if you want to stop by there and ask for some quotes, there will be some travel agents there to answer any questions.
Another idea you may want to try is the barbain finder here, just list the dates and the various cruiselines, number of people, city which you fly out of, if you want air included int he price. Then any travel agent will e-mail you back prices and you can compare. Its really easy and it does work, so give that a try too. Hope you find something that fits your pocket book and I think your kids will really enjoy it, expecially over a school break, many other teens to hang out with :-)