FMIL texted me today asking what the age cut off was for kids since her niece's son didn't get invited and he's 15. And????? What makes people assume their kids or a date are invited? The only person you should consider a package deal with you on a wedding invite is your spouse. I think it is so rude! Nothing against kids, but kids in general can throw the numbers out of control because if you let one come, you gotta let them all.
We went through a long debate of kids but the problem always came to we didn't want young kids (like under 13 say) but there were several families with a kid over the cutoff and one under the cutoff. You can't not invite 1 kid in a family! So we jumped to aunts and uncles and first cousins FI knows. We ran into an issue with second cousins who he really wanted there or who I actually knew and bonded with (due to his large family, his second cousins are more his age than his first). So we made some exceptions but with that text from FMIL I just told FI to play dumb and say we thought the 2nd cousins were 1st cousins. His family is HUGE and he doesn't know even half of them so I'm hoping playing dumb will work. Invitations have been out for 3 weeks now...at this point the guest list is closed for discussion IMO. If you don't like that we didn't invite your kid, don't come! Otherwise enjoy some kid-free time...that is important too!