I would encourage you to get there early or be ready to put your name on the list and be willing to wait upwards of 60-75 minutes for a spot. We had dinner on the night of the first
MVMCP a couple of weeks ago and were chatting with some people who were trying to come up for a bottle of wine, apps and fireworks (there were six of them, with two young kiddos) and they were quoted a wait of 45-60 minutes ... we saw them when they finally got a seat - in the couch area right by the glass with a GREAT view! - almost an hour after they put their name on the list, and 30 minutes before the fireworks started. So, the timing definitely worked out in their favor.
Cali Grill sends you a text message when your table is ready or your spot in the lounge is up, so then you can head to the check-in desk. You *might* be able to have part of the party skip over to MK for a bit (or at least stay there while one member of your party goes to get on 'the list'), and then have everyone be back at the Contemporary at the earliest possible time of the estimated wait (if that makes sense?).
But YES! GO! We did dinner on the 28th last year and it was lovely - the closer you get to NYE, the crazier it will get. Also, the lounge is not generally busy until the sun goes down (again, people want spots for fireworks), so if you go closer to, say, five or six you should be good!