Hi William,
Welcome to the Moms Panel! It's always fun to cruise with friends, and Disney Cruise Line makes it easy for multiple parties to stick together.
First of all, to book your cruise reservation I recommend doing it right from the Disney Cruise website,
www.disneycruise.com. This step-by-step is easy to navigate and understand. It even allows you to pick your own stateroom which can come in handy when wanting to be close to another family.
Once you have your reservation number, you and the other family should exchange reservation numbers and each call (800) 951-3532 to add a "traveling with" note to both reservations. By adding this information, they will essentially link your reservations, and ensure that you are seated together at meal time (be sure to choose the same dinner seating).
At this time the package rates for adding a stay at Walt Disney World before or after your cruise are not available through the Disney Cruise reservations (you'll notice during the booking process that the option to add resorts/tickets to your package is not yet available, this is only because the 2011 rates for WDW haven't been released). Simply keep checking back and modify your reservation to include the resort once this option is available. Personally, once the base cruise reservation is made, I find it easier to modify and change things by talking to a reservations cast member at (800) 951-3532.
I hope this helps!