What would they say indeed? After all, they are the ones who are responsible for this predetermined wedding. I guess, to them at least, it'll weigh up between:

how much they like Yuuhi + how much they honour their agreement
vs
how much they love Minato (it's strongly suggested they're not blood relatives. Minato said herself that she's adopted, albeit the "just kidding" right afterwards)

Knowing their dad though, I'm betting it'll come down to "A man walks his own path. Jun is old enough to decide himself!" *goes off to blow up some tanks*

And we'll be back to square one.