So on the Ticketmaster site it says doors open at 5:00pm for all 3 shows, but on the United Center site under their "miscellaneous" information, they say doors open 1 1/2 hours before a concert, which would mean 6:30pm. Does anybody know which is correct? When can we actually get into the building?

It probably states doors at five because of the Rebuild A Dream activities that will be taking place before the three shows. It it were not for that, I don't see any reason to show up more than an hour before a show.

There's a restaurant in the United Center. That's why the doors open at 5 - so people can eat there before the show.