I didn't really think that part was funny...
When Grandma Annie faked being ill and needed to go to the hospital near the end, she said "it was the only way I could get you both to shut up and go to the airport" or something like that.
It's not that I thought it was too far, I just didn't find it funny. She gets upset with them for talking to about what just happened at the altar and yells "stop it! stop it!"
Like sheesh, calm down. They weren't arguing. His dad just wanted to know what was going on and overreacts by pretending to be sick.