Mama Zooms

When a toddler sits on his mother's lap, he pictures himself transformed into a jockey racing across green lawns, a ship captain negotiating stormy seas, a smooth race car driver, a pilot whipped by wind in an open airplane, a train engineer peering down a dark tunnel. But this is no ordinary lap of pretend, because Mama has a ``zooming machine''--a wheelchair that transports mother and child to work and play and, best of all, far away realms of the imagination. Cowen-Fletcher's full-page pastel and pencil illustrations, frequently enhanced by the use of close-ups, depict within crisp outlines an energetic boy in changing costumes and appropriate positions on his mother's knees. A sense of motion that provokes joy makes it easy for little ones to join in the zooming from morning to bedtime, when ``Mama is just my mama, and that's how I like her best.'' With mother and son obviously relishing their every moment together, youngsters will warm to this unusual and commendable book--an unaffected portrait of a physically challenged individual. Ages 3-6. (Mar.)