another point to ponder on purchasing 2 cabins, we were going to do just that, but it ended up being cheaper to purchase 1 mini-suite instead of 1 outside balcony and 1 inside standard cabin.
on the suggested itineary - Eastern Caribbean would suit you perfectly, and on Princess leaving from Ft. Lauderdale you have 2 full sea days right off the bat before you cruise into St. Maarten. We loved having the 2 sea days right off - gives you a chance to relax, get into the "cruise groove" and get to know the ship.
after St. Maarten we cruised to St. Thomas - then another full day at sea until we reached Princess Cays (Bahamas). It was a great relaxing, beach itineary.