I've decided to extend my stay in Vegas slightly. Will be arriving on the 17th of December and leaving (7.20 am flight) on the 20th so I'll probably book a cheap hotel for the first two nights and one close to the airport for the last.

Thanks for the advice. Was a bit overwhelmed by options but I'm going to just choose one and book it.

EDIT: Considering how early my flight is and how much a room on a Saturday night costs, I might just stay out the whole night. Does anyone know if I can check a bag on Southwest a day before my flight (don't want to carry it around, and I doubt I can pick it up from a hotel at 5am)?