I love the idea of this.
As far as what games are a must,
Medieval Mayhem. No doubt about it.
As far as other games, I find that Combat or any two player game is fun when you have 2 or more people, of course.
I've tried to do things like this in the past, but where I live, there aren't many people interested in things that I consider to be "fun"...
While I was helping out at the comic & collectables store in town, I ran into a guy who had been doing D&D with the same group of people since they had been in school together. At least once a year they all travel from different stats and meet at his house to play. That's dedication to a game and to your friends. Not many people I know would make a trip like that. I'm not talking about single people either, these people all have kids and some even grand children and they bring them along! When I was a kid, it was rare if we even went to visit family if they were more than 30 minutes away!
I wish you the best of luck with the "Atari Party".