I'm pretty sure its 'Advertures in Babysitting" or "Adventures of a babysitter" or something. Starring a young Elizabeth Shue as a babysitter who has to drive into the city with the kids to rescue her best mate who has run away. The little girl's hero is Thor and is quite protective over him - her brother (Brad) takes the mick. I think it was released under a different name in the US ("Big night out??") Hope this helps.