We always check-in as soon as we arrive on property. We store our luggage with Bell Services. At check-in you will be given your room keys, your park tickets will be encoded on your room key, as will be your Dining Plan credits - one plastic card for everything. Yes you will be able to use your credits for a meal as soon as you arrive. If your room is not ready, you will be given a telephone number to call and check on its availability during the afternoon.
In October, we were checked in, had all of our documents, tickets, meal credits etc and on our way to enjoy Epcot for the afternoon by 12:45. Our room was ready at 3 PM when we called. At that time they give you the number of the room encoded on your key and you are all set. Either stop by Bell Services on your way to your room, or give them a call when you are in the room and they will promptly deliver your luggage to you.
Enjoy your trip!