Neville absolutely asked Ginny to the Yule Ball! Besties 5eva. As for Seamus, Neville has NO IDEA how to handle the flirting. He might smile awkwardly and thank him. Because awkward.
Remus will love her back. So sorry on your oops pregnancy. That's a bummer. If she needs an ear, Remus will be that for her as well. In case she wants to avoid the immediate fam for that.