My dad is splitting the cost of the wedding with my mom and my FI's parents. He just sent me an email saying he forgot to add a couple of his friends to the guest list (who I don't know). At less than two months to the wedding I feel like the time it would take to order the extra invitations, send them to these people, and get their RSVPs back, would put me past the deadline to tell the venue how many guests are coming. Is it appropriate for me to reply that I hope he understands, but at this point the time constraints don't allow me to invite extra people? The venue has enough space, and a month ago or so he sent a similar email about a different set of friends he had forgotten to invite and I accommodated him, but at this point it's time that I'm more concerned about.