After Lorraine (Hillary Duff) graduates, and Nora (Piper Perabo) announces that she is moving, Tom (Steve Martin) and Kate (Bonnie Hunt) are sad to find it that their children are leaving. Tom takes the Baker family to Lake Winnekta during the Labor Day weekend. The Bakers end up getting competitive with a rival family, the Murtaughs. Tom Baker really wants to win this year, will they?