Welcome aboard, Alecia! I'm so happy to hear that you are considering a magical Disney cruise for your family!
While the 2014 Halloween plans have not yet been released, I would guess that they will be pretty similar to what will be taking place this fall onboard the ships. This year, the Disney Dream will feature extra special spooky cruises throughout October with their
Halloween On the High Seas sailings. Families of all ages will be in for lots of family-friendly scary fun on the Dream including trick-or-treating, a special Mickey's Calling All The Monsters Mouse-Querade Deck Party, The Nightmare Before Christmas interactive movie event, other Halloween movies, themed crafts, activities and more. Expect pumpkin carving and a Disney villain takeover of the ship announcements (yikes!). These events will absolutely be appropriate for your 10 and 11 year olds. In fact, many of these events will be geared to them! They'll be able to have even more fun in Edge, the tween club, where I bet there will be some Halloween themed activities going on as well! Costumes are a must for the family as even the Disney characters will be wearing their Halloween gear!
Disney's other three ships, the Magic, Wonder and Fantasy are offering some spooky fun as well, though not quite as much as the Dream. There will be haunted parties, costume parties, spooky movies and ghoulish delights. Of course, you'll want to have your camera ready on these ships too, since the characters will surely pop out to visit in their Halloween outfits!
I'm sure you'll find the weather to be nice and warm in the Bahamas and Caribbean in October. We've sailed at all times of the year with Disney and always have found warm, even hot, weather even when it's fall and winter.
I hope that helps as you continue to plan, Alecia! Let me know how else I can help!