I think the more important part would bother me more if Emma were a child. Children always have to be put first. But I don't think that is necessarily true once the children grow up. Part of being an adult is being on you're own and fending for yourself. Family relationships change when children grow up. The parent's job for adult children is not to care for them in the same way. It becomes more of a friendship relationship, though not exactly the same. And this is even more so I think in this case since Snow and Charming didn't raise Emma.

So I'm okay with Snow choosing to stay with Charming who would have been alone otherwise when Emma was an adult and had Henry and would not have been completely alone.