That Old Feeling (1997)

Lily and Dan are a couple who have been divorced for years. When their daughter, Molly gets married she invites them. At the reception, Lily and Dan bicker loudly so Molly asks them to leave. It's while they are alone that their banter turns into passion and they get it on. Later while Molly is having her wedding night she discovers her parents together and freaks out. The next day they run off and their partners are wondering where they are. Molly decides to try and find them and she enlists a paparazzi who's been following her mother to help find them.