I will say this, guys are generally more open about fetishes, and accepting. If he already accepts diapers, that tells me he is not some mean, crazy redneck. So I bet he will be willing to try it. I also think asking a Man to be a Daddy is a heck of a lot easier then asking a woman to be a Mommy..... You will need to define some parameters, and if he decides its not something he is crazy about accept limitations.