He. His and Jenny doesn't make sense, him and Jenny doesn't make sense, and we and Jenny doesn't make sense either so it's He and Jenny are going to ride in his car.
Gertrude Stein, patron of the arts, was a voluble conversationalist when artists and writers visited her Paris apartment in the 1920s and 1930s.
Form google dict., voluble means <em></em><span><em>Speaking or spoken incessantly and fluently.</em></span>