The Blue Bird (1940)
starring Shirley Temple (RIP)
IMDb synopsis:
Mytyl and her brother Tyltyl, a woodchopper's children, are led by the Fairy Berylune on a magical trip through the past, present, and future to locate the Blue Bird of Happiness.
The Blue Bird (1940) - IMDb
It also might be in the 1976 remake.
Here's the scene from the 1940 film:
The Blue Bird 1940 part 8 of 10 - YouTube
EDIT: There's another movie in which people fall in love in Heaven then come to Earth, but they're portrayed by adult actors: Made in Heaven (1987)
http://www.imdb.com/title/tt0093467/