I have a 14-month-old dog and a 9yo with anxiety, self-regulation concerns, and mild inattentiveness. I researched the heck out of breeders and really focused on temperament in the line (among other things, but this was #1 for me). I also have 2 teens. While I think we were naive in what having a puppy is like (oh my, lol!), I feel like our experience would have been very different if my 9yo didn't have anxiety/impulsivity/inattentiveness (it's ADHD w/o hyperactivity).
It's been a constant challenge in training. Hard enough with 5 people in the house/being consistent, but the 9yo has made it beyond challenging. The two can barely co-exist because it always seems one of them is in a heightened state & gets the other one riled up. My child is kind, loving, sensitive, thoughtful. Our dog is a normal, happy, social adolescent, who is probably better trained than many 14-month-old dogs (because we have used a private trainer for about 20 sessions over the last year plus puppy school). And yet this last year has been a hardship beyond what, I believe, other "puppy families" experience. We're starting to come out of it--may be because my child is older and is responding better to what to do/not do around the dog and/or because the dog is responding better (consistent training, recently neutered, generally more chill). But my husband and I have quietly said to ourselves over the year that we wish we had gotten an older dog.