Other mistake: At Paul's wedding, Paul gives a speech saying that Connor was always there for him, "ever since our parents died when I was 2 and Connor was 7". However, in the scene showing when Connor and Jenny were just kids and she gives him a camera for his birthday, Jenny and Connor appear to be at least 10 years old - certainly not 7. Connor tells his ghost, "that was the summer before my parents died". The scene that follows shows the parents funeral, with Paul sitting next to Connor, and Paul appears to be about 5 or 6 years old - but much older than 2.
Continuity mistake: After the cake is destroyed Jenny is attempting to fix it. As she and Brad are talking, the camera switches angles viewing Jenny from the front and side. In the shot facing her, her hands are covered in cake icing, but in the side view there is little to no cake icing. It is continuous throughout the scene.
Character mistake: If you ever called a Marine Sergeant Major "Sarge", he would probably kill you. It just wouldn't happen. That's an Army thing. Also, Marines say "ooh-rah", not "hoo-ah". That's also an Army thing.