A melting-pot gambol with more spirit than substance--but not a dull moment either. Stirring up the social mix is eleven-year-old Maggie's irrepressible Grandma, who takes off in a borrowed station wagon--with several of the N.Y. walkup's trouble-beset kids in tow-to prevent snooty Aunt Ruby from taking orphan Maggie away to a better-class life in California. En route to the ""beautiful big"" Mountainside house of a cousin Grandma hasn't seen for decades, the travelers change the lives of all and sundry (sample: Grandma persuades a decamping young couple to turn their yard sale into a wildly successful antiques-and-crafts mart, which encourages them to stay put). Meanwhile, the police are trying to track the station wagon down--surely not just on account of Aunt Ruby Cousin Esther turns out to be a near-derelict, the once-spanking house a local eyesore, targeted for demolition--but count on Grandma's resourceful crew to salvage both. There's stolen jewelry in that thar get-away car besides, and a providential reward for same; and to make the ending totally happy, sour Aunt Ruby smiles on the lot of them. Harmless if not taken seriously.