You can sleep in a little and eat on deck 9. My only suggestion is to be off the ship before 9 so that you don't get put on the last bus.
The "normal" buses go to 3 resorts each, all in the same area (like EPCOT area resorts). They depart as soon as they are reasonably full. You are not assigned in advance to a bus or a time; there is a CM as you enter the bus area who asks where you are going and sends you to the correct bus.
The last bus.....will go to as many resorts as it needs to. We were on one bus, and our dinner partners were on another. We sat for like 20 minutes, and then they were getting onto our bus with shuffling of luggage, etc....and a while later we were all on the way to WDW. We overheard the driver complaining to the CM that he had 6 resorts to hit now. We were lucky--we were the first stop! There just weren't enough people to justify 2 buses, so they combined it. We were off the ship right at 9 that time. The last bus will not leave till they are sure they have everyone. We didn't leave till about 9:40 after sitting for 20 minutes and then doing the combining thing.