That is so awesome! I so want one I'm in love with Biology (and my Biology teacher I think I'd like to make her one too). But while I'm thinking about it can you post the picture or the link to the picture you found - I can't seem to find a good animal cell thing.
You could have people dress up really nice or you could go to thrift store and buy old dressy clothes, etc and play dress up - I guess that would kind of go with the dressing room thing. My friends and I love to get all dressed up and stuff.
Ahh! My birthday is December 14th too! But back on topic, I like your hotel room idea and even though your friends aren't craftsters doesn't mean you can't have crafty things set up. You could get cameras and take pictures the whole night, but during the party make frames or something then get the pictures developed and use some of them. And since you're starting early - there's plenty of time to save money and look around for cheap stuff to do. like going to sales and what not and getting fun stuff to do. I'm so cheap i buy almost everything on sale and don't forget local thrift stores.
P.S. Even though you think scanvenger hunts are lame, you could have a lot of fun with it. Make a list of wacky items or things to do.