The father builds up a shelter below the house in case of there is a holocaust. The shelter is filled with all the necessities to keep two of them alive for a long time.
One day a plane drops a bomb just near to their home and they think the holocaust had happened and went into their shelter.
That's all I have I don't remember the cast or the time of production, but I sure that it was related to WWII.

Blast from the Past (http://en.wikipedia.org/wiki/Blast_from_the_Past_%28film%29)?