Ah he is so cute is he a Jack Russell? How old is he. You have cute kids too.
Buddy Boy loves to play with Jack Russells; they can match his energy level. Also Jack Russells have that terrier thing. They are sure of themselves and not easily scared. Buddy Boy respects that in other dogs.
Fern the Elwood the cat has a slight weight advantage on Buddy Boy the dog. However, Buddy Boy is fearless and kind of crazy. He would never hurt the cat, he was only 4/5 months when we got him so he was raised with the cats. Elwood is older and Buddy Boy keeps wanting to play with him. Elwood is about 14 years old is not interested in playing. Enter my other cat Charlie who is about 4 years old. Charlie loves to play with the dog.
In the case of Charlie and Buddy Boy. I would give it to Charlie, he has his claws (I don't de claw my cats) and he is lighter on his feet. When he is done playing with the dog he goes up high and stares down at the dog. Buddy Boy hates that.