Hi tiggermiller's mom!
We stayed at the AKL last week - four awesome nights! (Oct 17-21) You may be cutting it a bit close....
Our recent experience agrees with C&D... the bus ride IS about 12-14 minutes. But, you need to consider that the bus may not be there (at AKL) right when you need to go. Ususally the wait is pretty short... 10 to 15 minutes at the very most. Then there is walking time from the bus after you arrive at MGM to get to the main gate, go through security etc. Then the little walk to check in at Fantasmic. If everything goes perfectly, you should be ok leaving at 4pm. I'd personally leave AKL at 3:45 though.
Darian