Hi Sarah,
Welcome to the Moms Panel! I'm super excited about the newest ship, the
Disney Dream, setting sail in 2011. Personally I typically book all of my cruises by visiting
www.disneycruise.com. Their cruise finder makes it easy to book your cruise step-by-step, and currently they are offering a $25 on-board credit for staterooms booked through the website.
In this instance however, since you are booking for six guests (and I assume you will want connecting staterooms) it might be easier to call the reservations line instead at (800) 951-3532. This will wipe out the $25 on-board credit from DCL, however if you pay for your voyage with a Disney Visa credit card, you will receive a $50 on-board credit - even better!
When you call, I suggest that you have your computer on and your browser open to www.dreamsunlimitedtravel.com because they have a nice "deck plans" section that gives nice color-coded layouts of the ships decks. You'll be able to see exactly where your stateroom will be.
Whichever way you book, I wouldn't wait. Easter break is often one of the most popular weeks for family vacations to Walt Disney World and on the Disney Cruise Line.
I hope this helps!