Hi there, Julie!
By all reports,
Disney's Art of Animation Resort will have its own dedicated bus transportation to each of the Parks, the Water Parks, and Downtown Disney.
That said, it is a large Resort, and you will want to allot plenty of time to ensure that you'll get to the Magic Kingdom to grab a great spot for all of the incredible nighttime activities to enjoy.
I would suggest booking out a minimum of two hours from your arrival at the bus stop by the main building. This way, even if you have to wait for a bus, you'll have built in enough padding to accommodate any delays. This also factors in travel time and time you'll need to pass through ticketing, the bag check, and that first delicious Mickey bar!
Perhaps it seems excessive, but two hours is a nice window that largely guarantees a stress-free experience. Once you have tried it, of course, you can tweak the time to your liking.
Have a great trip!
See you later, celebrator,
-Deborah B.