As others have noted, the summit house is small and will be very crowded with all of the extra folks up there due to the race. The view of the race from the summit house is effectively zero. While it is a bit warmer, the air is just as thin.
If your family will be showing up to spectate, then it is best to plan on being outside where they can actually be spectators and watch you come up the last few switchbacks and cross the finish line. If they bring a warm jacket, a hat, and some snacks then they can sit on a nice comfy rock and start cheering for the other runners starting a little after 9 when the first runners hit the finish line.