Definitely do the tour of Lambeau and the Hall of Fame. It's a beautiful stadium and should be really impressive with the new addition. I didn't get to see it last year on our abbreviated Packer Shareholder meeting visit due to a family emergency. But from a distance it was pretty spectacular. I'll see it in person in three weeks at our preseason game.
Game day, allow enough time just to wander around and take in the sights, the fans and the colorful characters. It may be tough tailgating as you're flying in, but there are plenty of places to eat nearby or at the Packer Tundra Tailgate Zone. Check out the Packers Website for Gameday info too.