Seventeen Again (2000)

Gene and Cat have been divorced for several years. They are both visiting their son and grandchildren, Sydney and Willie. Willie's a genius who develops a formula that makes who uses it young again. It inadvertently spills into some soap that Willie places in the guest room. When Gene and Cat use it they finds themselves 17 again. Willie has to find a way to reverse the process. But will Gene and Cat want to be old again?