Welcome aboard, Carolyn! You sound just like I did a few years back! Our family had visited both the Disneyland Resort and the Walt Disney Resort many many times, but had never cruised with Disney, and once we did, we were hooked! You are going to really enjoy your experience with Mickey and friends aboard one of Disney's pixie dusted ships!
The best prices are usually available when the new itineraries are released. Currently, Disney Cruise Line has the itineraries out for sailings through mid-2014, so I'd expect the second half of 2014 to be released soon, but no one really knows exactly when that will occur, so keep an eye out!
If you have children, you will want to watch out for the Kids Sail Free promotions that Disney Cruise Line offers occasionally. Most likely those will be on either the Magic or the Wonder, and during winter or early spring sailings. Last year, we had a February cruise on the Wonder booked. About four months before we were set to sail, our cruise became listed in the Kids Sail Free promotion, so I called Disney Cruise Line to adjust our rate. We did switch to a different stateroom, as only certain rooms and categories are valid for that promotion. But, they were happy to help us switch and cut our price!
Occasionally, you may also see an On Board Credit promotion being offered through Disney or quite often many travel agents will offer you an On Board Credit for booking through their agency. Other than that, I don't expect to see many other promotions unless you are a local resident in the port area, such as Florida. Check the
Special Offers Page of Disney Cruise Line's website often and hopefully you'll see a nice deal pop up that will be just right for your family! Good luck planning, Carolyn, and please stop back here with any other questions, as I'm always happy to help!