Hi Darci,
You're going to LOVE Walt Disney World in March! It's my favorite time of the year gto visit. The flowers are in bloom at the Epcot International Flower & Garden Festival and the weather, in my opinion, is just perfect.
There is a special offer for free dining for guests planning a stay in early or late March 2012. You can see the details of that plan
here. Unfortunately, the dates of your upcoming trip are not covered by the current promotion. Is there any chance your dates of travel are flexible? If so, you might want to visit Walt Disney World when free dining is available.
If you cannot move your travel dates, I would suggest that you book your Disney resort now. If a new promotion is offered between now and your trip, you are certainly welcome to re-book your vacation under the new offer. That should be no problem. I would further recommend that you work with a Disney-savvy travel agent who will help you keep your eyes open for new offers. You don't want to miss any new deal that might save you some money on your magical Disney vacation.
Best wishes as you plan your sisters getaway! Let us know if you need any additional advice. We'd be happy to help.
Jill