You can change the household name under "My Households" in Manage Worlds. You can change the name of the lot in Build Mode (there is a box at the top left of the screen).
As for last names, I think it takes time for the game to process, even if you have it set up for one partner to take the other's last name. I am also old-fashioned, and have MCCC set up for the female to take the male's last name, but I've noticed once I marry one of the adult children off, the female doesn't have the husband's last name right away, but eventually it shows her as having his last name. You could always also change it in CAS full edit mode. Hope that helps!
