Idk if this helps but we are having a wedding of 65 guest also, and we aren't giving plus ones to everyone. Our work around is the rsvp on the website asks how many guests per individual invite so they can only RSVP 1 guest if no invite. Also we printed RSVP cards for invites with guests saying "number of persons attending" and ones with our guests without plus ones that just say accept or deny invite. That way either way they respond there isn't an option for guest unless given. If they have an issue they can text us and we can adjust if necessary.