Hi Stacie!
There are lots of things that you can do on your arrival day that don't require park admission, but will definitely give you a big dose of Disney magic to get your vacation started.
A popular choice for a lot of people is a visit to
Downtown Disney. There are lots of restaurants, unique shops and entertainment to keep you busy. One of the newest additions to the Downtown Disney area is the Characters in Flight hot air balloon experience. This attraction gives you a taste of what a real hot air balloon ride would be like and offers panoramic views in all directions.
Another option would be to visit
Disney's Boardwalk. In the evenings there are street performers, live entertainment and even midway games. There are also lots of shops and restaurants here.
Finally, you could book dinner reservations at a resort on the monorail line and use the evening to tour all of the resorts on the monorail. It's a great chance to check out the different resorts and get an idea of where you might like to stay one day. Simply riding the monorail will make you excited to be at Disney World!
I hope this gives you some ideas! Enjoy your upcoming vacation!