You'll love it - best thing we did for our family.
We took our 14 month old last May. Here is our trip report which has lots of tips in it:
http://www.disboards.com/showthread.php?t=570103
As well as our slide show on our website:
http://homepage.mac.com/alysa.kim/thekimsatdisney.htm
You'll probably get a lot of tips from this board but here are some of ours:
1. Bring baby's bed linens and bumper for familiarity. Don't skip naps! If baby has a schedule at home, try to stick to it.
2. We loved the Animal Kingdom Lodge but would never stay at Disney without access to a kitchen again! Having one a Vero was so great - we saved a TON of money and it was only once we got to AKL and we couldn't give DD the food she was used to at home that she went off her food and started eating only grapes and macaroni. When we stayed at BCV this trip (our favourite resort so far) we were able to eat at home when we wanted and then go out several meals that made eacch one special for not being every breakfast, lunch tea and supper.
3. A surfer style bathing suit is great for keeping baby's skin protected.
4. Further down in that trip report is a post I made about making an autograph album. We took it with us again this past April and it was worth every moment it took to put it together. The characters loved seeing their own pictures and it made for some great interaction both trips.
We are taking our daughter again next March with her new baby brother or sister, her grandparents, and my sister and her family. She is already talking about it all the time. "We go in March!" she told her day care teacher, who said to us, "That is so nice, kids should wait until they are old enough to enjoy it there". We just smiled at her, and laughed about it on the way home. We were too embarrased to tell her that DD has gone once a year since birth and loved EVERY minute of both trips and still talks about them to this day. She LOVES watching the slide shows on the computer and looking through the albums and she gets quite annoyed when she looks at the album from before she was born and can find pictures of everyone in her family except her and her cousin who is the same age as her (18 of us at the BWV Grand Villa - now that was a trip!)
Anyway, enough rambling. I envy you your first trip together as a family - ours was so wonderful. Every trip is, but that one was different - magic - it was like after so much hard work and sleep deprivation that it was the first time we could just enjoy that brand new, emerging personality. Great family time. You'll see what I mean when you go. Sniff! Enjoy!
PS. Speaking of family time, don't forget to take a pair of plastic champagne glasses and pick up something nice to drink and some gourmet goodies at the Publix - those afternoons and evenings spent together as a couple out on the balcony while DD napped were a wonderful, romantic way to reconnect.