How far is the hotel, and what hotel is it?
You could park at the hotel and take the I-Drive trolley to the convention and back. They would almost certainly let you park in the morning, even before check-in time.
Or, the hotel might have a complimentary shuttle to the convention center.
There's a lot of food along International Drive that's a short walk (depending on your costume) or to which you can take the trolley.
Thanks to DavinDaLilAzn for suggesting this in another thread.