You all have such great etiquette advice that I wanted your thoughts on this. We are still a few months away from sending out StD's, but I am ordering them soon and plan to send them out basically as soon as flights are able to be booked. However, I realized that we might have a bit of a sticky situation with some of our guests on FI's side.
He is adamant about having no kids. He conceded a bit on my one 9 year old cousin (we are inviting her parents and her two adult brothers, so it didn't seem right to me to not invite her because I didn't want to split up a family; she will probably be a flower girl/junior bridesmaid as well), but other than her we are not inviting kids under the age of 15 or so. We aren't splitting up families; this is just how it worked out, as all of the kids on my side apart from my one cousin are high school age or older. His side has very young children (under 7), but we only plan to invite the parents per his request.
He has an aunt, uncle, and two young cousins who live about a 5 hour plane ride away from where we are getting married. Her and her husband are on our guest list, but their kids are not. I plan to only put her name and her husband's name on the Save The Date, but I'm not sure if that will get the point across, and would feel terrible if she books flights for her children as well. The flights will probably be booked prior to invitations being sent out. Is there anything else that we can do without being offensive to let them know that only the aunt and uncle will be invited? I can't think of anything from an etiquette perspective, but would like to prevent an awkward situation from occurring if possible.