Post-wedding party for family friends only

Personally, I think these people will be more offended by the idea of a separate 'celebration of marriage' event than they will be by you not inviting them to the wedding.

These people will learn of your wedding at some point or another and if you invite them to this separate party after the wedding, they will probably feel b-listed since they were invited to that event but not the wedding itself.

I'd feel pretty left out too if I was invited to a separate occasion. Perhaps your parents would be willing to contribute to the reception so that you can expand your guest list?

It depends on your family culture. This is very common practice in other cultures, especially in Asia. Those who are invited in the 2nd party aren't offended because they understand that there's only a limited number of people the couple can invite. You better discuss this with your hubby so you can at least think how others would feel.

It's always fine to throw a party and invite people. Parties are nice! But you don't need to specify that it's wedding related (because it's not really related, several months later). Once you call it out as a "wedding celebration" then you put people on the hook to bring gifts and that could be awkward. But if you just invite people you care about to a party and host them with nice food and drink, everybody wins.