But I'd say Naveen, he changed a lot after Tiana and he was about to sacrifise his love for her and marry someone he didn't love just for Tiana to have her restaurant.
So, I think he would do it, if Tia's father would live, not only for Tiana but for peace (were he in John Smith's shoes).
My second choise would be Flynn, since he gave up his own life for Rapunzel's freedom.
But IMO I am not sure if anyone except John Smith would do it 10000%.
I am sure everyone would sacrifice his life for his love but not his love for his father's love. That's way too much.

Aladdin, Beast or Shang.

I think Eric will do it to save Triton. He's kinda selfless.

and Aladdin

I think they all would, but mostly Shang, Aladdin, Eric, and Beast

Shang knows what it is like to loose a father. Surely his past, braveness as a general, and his love for Mulan would make him save her father.

Or Beast or Flynn

Shang is incredibly protective of people he loves and of people that are dear to the ones, plus he is noble and he considers protecting people to be his duty that's why he would do it for Mulan's dad without asking questions.

I can see Eric doing it for Triton and also Flynn would probably never let anyone hurt Rapunzel's family seeing how happy she was when she reunited with her real parents after enduring years of Gothel's emotional abuse. He'd rather die than see her miserable - in fact he already proved it by sacrificing his life so she could be free.

Eric...or maybe Aladdin

Shang for me seeing how one he lost HIS father too the war his love and respect for Mulan and admireration for Fa Zhou he would do that no questions asked plus when Mulan was discovered when she told him why she did it he understood and allowed her to live because he felt that because she had saved his life and her selflessness she has for her father thats why Shang is my choice he lost his father and would not let Mulan know that pain