Aurora is mostly correct. The arc of the convention is that "Hostility" will open on Thursday night for people to pick up their membership packets. It's a good time to meet folks and hang out with early arrivals. The ICG meeting is tentatively scheduled for Friday morning, with light programming opposite of it. Monday will also be lightly programmed up until early afternoon or so, I expect.
In the evening, I also anticipate the stragglers will go somewhere for dinner. At CC16, we had over 40 people descend on a local Mexican restaurant and everyone had a great time. Then, the 3rd ever Mousekerade is supposed to happen back at the Hostility Room again. So, the Dead Dog party is a good time to relax and talk with people you've met over the weekend (this is a really good time to talk to the Old Guard). Things will eventually wind down and people will be driven from the room at some point, I suspect.
If you can come in early and/or leave late you can take in some of the local tourist stuff like the Arch, sample some Ted Drewe's frozen custard (I think they'll have one of their stands open, anyway, despite cool temperatures), the Zoo, Grant's Farm, the Art Museum, etc.