The desk where you make reservations closes at 8pm so you'll need to wait until the next day. Drop your stuff in your room and go get dinner at Bella Vista or order room service your first night. Tuesday and Friday nights are event nights and there are no reservations for those nights. There are only two restaurants that require reservations so I'd recommend going back to the lobby on your first morning (you'll want to find your way around during the light of day anyway) and making reservations then. That way you can ask questions directly. You need to pick times and if you want to eat inside or out. I believe you'll be able to better make these choices after first seeing the lay of the land, and looking over the event and activities schedules and figuring what else you'd like to be doing. We never made reservations more than a couple days out and it was no problem.
Hi! Since you get in late on your first night, Bella Vista (the Beach Grill) is the only non-reservation option for you. It's lovely you can have a nice dinner on the beach and listen to the sound of the waves and the tree frogs...Or if you don't feel like leaving your room, you can order room service.
On Sunday, you can call Guest Services from your room and make your dinner reservations. I think they open around 8am.