The House at the Edge of Time — Pat Pflieger

Some houses are bigger than they look! Max has a problem: he's the new kid in school, and nobody wants to be friends. Until Ran invites him home. And that changes Max's life. Because Ran has a secret: his family has a time machine. And his uncle is lost somewhere in time. Can they rescue Ran's uncle? Can they FIND Ran's uncle? And can they get the dinosaurs out of the house?