I know that this can be a very sensitive issue for many so just wanted to see how others would handle this. FH and I are in out 30's (been together 10 years) and we have a LOT of friends and family with young kids that we love to death but we have decided to limit the guest list to adults (not because we're afraid kids will be kids but because 1. that would be 30-40 additional guests on top of 125 adults and 2. our reception is an outdoor tented reception next to a river and that scares me to think of kids running off in the dark by water) The exception is FSIL's daughter (our flower girl) and her little brother or sister who will be born the month before the wedding.
So my question is regarding the children of a distant cousin. Her older daughter is in her 20's and has a severe disability and her youngest is a 5 years old who I have met several times over the years and she is a wonderful kid. FH and I would like to extend an invite to their whole family because I don't think it's right to invite the older sister and not the younger. Do you think I should give them a heads up that the only other child invited is the flower girl or just send the invite? I don't know if someone would feel weird showing up to an event where they had the only non wedding party child. I'm sure I'm overthinking this...