Look at the time for Wishes on those nights. If Wishes is at 9:00, make an AR for 7:30. Get there thirty minutes before (7:00) and tell them you will wait for a window table. If you happen to get a window table closer to 7:00, you'll have to stretch dinner a little to see them at 9:00, but chances are you will have to wait at least 20 minutes for a window seat to clear. If you have to wait longer, that's ok, you can browse in the gift shops.
Or, you can make a reservation for 7:00, sit anywhere and then walk down to the beach. If you sit close to the pool, I believe you can still hear the music as well. We've seen them from 'Ohana and the beach and really, they are both good.
Yes, you should have time to hop a monrail to MK and catch a bus.