am I able to book a room for a small party

Yes the have small ball/conference rooms.

Overpriced

Yes

I would think you could!

They had a huge convention 2 weeks ago, and i remember seeing unused rooms

I don't see why not; they have many single rooms that can be booked. However, you would have to find a weekend when those rooms aren't involved in a hotel-wide event and that might be the hard part. You would have to call them for that.