Hi Julia,
You'll have a blast on a Disney Cruise - they're great for families! If you know which cruise itinerary and date you want, try Cruise Compete. You will submit a request and hundreds of cruise agents have the opportunity to bid for your business. The Cruise Compete service allows you to stay anonymous throughout the process. It's a neat service. You can also get a good feel for prices by checking out some of the large online cruise agencies such as Vacations To Go, Cruises.com, Cruise.com, etc. Let me know how it goes - I can't wait to hear all about it!