You will have a blast! We took my daughter at 14 months and it was great. A few things I'd recommend...
- Make sure you take a stroller that is both comfortable enough for her to nap in, but also collapsible enough to manage on the buses and trams. We used a Peg Perego Pliko for Disney Duty until our 2nd came along.
- Be prepared to change your pace... Remember, she will be taking in all the sights, sounds, and smells of the World, and a stroll down Main St will be just as much of an "attraction" to her as a ride will be. Trying to do too much too quickly might overwhelm her.
- Scope out potential nap places ahead of time. Our daughter always had a hard time falling asleep in public (as opposed to my son, who at 18 months can fall asleep anywhere!), so we went in with a general idea of a few quiet corners in each park where we could park to let her fall asleep.
- On the subject of naps, don't be afraid to head back to the resort for an afternoon nap. If your baby is usually an early-riser, head on over to the parks early in the morning, and plan to come back once naptime rolls around. Once everybody is refreshed (mom and dad, too!), go back to the parks for the evening.
- Have at least one date night. Since you'll have "helpers" with you, plan a nice dinner for you and your husband. It's supposed to be a vacation for you, too!
