I think Fates was on the right track with the inclusion of the Avatar as the main character, but the execution was just so, so bad. So, if one must be included, I wouldn't mind them trying that route again, so long as they're well-written and the choices we make actually mean a damn thing. I actually like marriage. I think it's fine for the Avatar to support with everybody, but conversely, I want to bring back limited support pools for the other characters.
Children I'm on the fence about. I liked my kids, but not anyone else's. If it's something that needs to be sacrificed for the integrity of a good story, then so be it.