UPDATE:
I bit the bullet and was honest with my co-workers. I told them that I had originally invited co-worker #1 to go so I would have some company and not be alone (this was perfectly fine with my boss, he usually encourages me to take the family and make it a vacation/business trip). I then explained how it just wasn't feasible to have 3 people in a King room and I didn't feel comfortable with them staying up partying at night and then bothering me when they slink back into the room.
I could have probably gone to my boss and had him sort it out, but I feel like I'm a big girl and got myself into this mess, I have to see my way out of it.
The co-workers were really pissy but said they understood. Oh well, lesson learned, no more inviting co-workers on my business trips. It will probably be a little uncomfortable at work for the next few weeks, but I'm sure it will blow over.
Thanks for everyone's advice, I appreciate it.