Call the front desk at the hotel and I'm sure they can help. Make sure you let them know A)In advance and B)That you are a young teen trying to make this special so your budget (if I'm not mistaken) is probably pretty limited.
We have had both my grandparents' and parents' wedding anniversaries at Disney. They do an INCREDIBLE job. They will decorate a small area of the room possibly for when you arrive, or one of the nights while you are out of the park. For my parents, they gave us a picture (authentic photograph) with all the characters' signatures ...from Cinderella to Pooh to Mickey...in a card that wished them Happy Anniversary, along with a small cake and something else that I can't remember.
For my grandparents, they had a white chocolate Mickey structure with details you couldn't even comprehend with all sugar structures around it...one of the coolest things I've ever seen. Looked like glass. On the beds they dispersed rose petals in heart shapes and randomly. I also think there might have been balloons. It was so incredibly Disney-esque and magical.
So therefore, call the front desk of your hotel, relate these stories or give ideas that you may have of your own...it's Disney...if you can dream it, they can do it.
Hope that all helped! PLEASE let me know how it turns out. Really! I'd love to know!
I would suggest finding an inexpensive 
Feel free to pm me for any "real" suggestions! Also ask around on the Restaurant board for some great restaraunts to go too..
