I've looked around on other posts, but I haven't seen an answer to my specific question. If it's already on here somewhere, forgive me

I am an elementary teacher, so I do really like kids, but because of budget/guestlist/etc reasons I don't think I should have them at the wedding. HOWEVER, my aunt is much younger than my mom, and her children are both in school (one in 8th grade, one in 4th or 5th). They live out in Colorado and would need to fly in for the wedding. Of course I want them there! I have a very small family so I want as many as I can get to be there!!
My question is, what would be your cut off date for a young person to attend or not attend the wedding? I don't want anyone to see them and wonder why other kids couldn't be there, and I really don't have a problem with older kids- I just don't really want the young ones there that haven't learned to control themselves yet.
As I write this, it seems silly, but still- could you limit your list to PG-13 or double digit ages only?