Old dog is young again

Almost since the day we got Kody last February, he has tried to play with Tawny (my 14 yo dog). Tawny has wanted no part of it. He bites at her legs, she tells him no and tries to get away. In the beginning, I was forever telling her to sit on him. Now in the last day or so, he has started the play, but she is all in there playing too. He leaves and she chases. It's a loud thing with both dogs barking. LOL right now she is biting at his back legs!