Why would anyone suggest anything other than asking the host? It’s not a test, and asking the host is not cheating!
Exactly. Of course this was asked by a guy who has yet to figure out how to use Google. Baby steps.
Pick the kid an entree. Regardless of seating a 15 year old deserves proper food.
If there is no menu choice for the kids, they are probably getting pizza or chicken fingers. I’d pick an entree and see what happens.
Pick an entree, and sit where you find your place card.
Regards,
Shodan
Ask the hostess.
That said, I’m a children’s author and read a lot of stories about Thanksgiving in various magazines, and “the older kid forced to sit with the younger ones” or “the older kid sitting at the adults’ table for the first time” are very popular story themes. In the former, the older kid becomes the leader of the kids’ table and has a great time and gets respect! In the latter, the older kid is bored to tears at the adults’ table and decides to switch to the kids’ table and has a great time and gets respect!
I second this. I come from a large family and at my own wedding, the kids table consisted of the 7 youngest kids at the wedding. 2, 7, 7, 8, 9, 10, and 15 (the 2 7 9 and 15 were my siblings) but that was just the way it ended up. The next youngest were 17-18+. We felt bad sticking #15 at that table but we talked to him about why, bought him a discman (not just for sticking him at that table), and he even ended up getting a little bit tipsy from everyone giving him alcohol while teasing him for being there (he gets ill at the smell of peach schnapps 20 years later). His holding it against me/us occasionally came up at family get togethers (“Do you remember how Disheavel put me at the kids table?”).
So I was highly amused when he got married last year in NY in December (important later) and we (my wife and children) went to find our table and it was table #99. We searched the room for Table #99 but the highest in the room was ~#30 so we asked a server. She chuckled, said something like “Oh it’s you guys.”, and led us to the wedding planner who led us outside the venue to a nearby patio/deck with the large windows between us and the party inside. Meanwhile, my brother had grabbed the microphone and was telling everyone inside about exactly why we were seated outside in 20˚F weather. After we sat down as we got it immediately after being led out the door and played along- waving inside to everyone. We then got ushered back indoors to our real table so that he could “be the better brother!”
So yes the kids table is the flexible table, but don’t let it bite you later 
Geeze louise, because my family is so long lived, I’m in my 60’s and still stuck at the children’s table. What we ‘children’ do is sit side saddle on our chairs and hop up when our names are called to wait on the 80 and 90 year olds.
If they’re gonna foist chicken nuggets on a 15.5 yr old the poor kid would be better off not going.
Good advice here! Thanks, all! …and, I’ll let Dear Abbey and Miss Manners duke it out! 
Has your daughter been presented to society? If not than she is still a child.
She is only 15. She is a child and should sit with the children until she is an adult at age 18.
I agree that the hosts should be asked. If your son has a preference, mention that, but at the end it’s the host’s decision.
See, I was the opposite. I was and am awkward around kids in the 6-14 age range (though I love younger children and young adults). I always did prefer the “adult” table, which was rife with joking and political talk.
Argh, missed the edit window!
DAUGHTER, not son. Mea culpa.
None of our family weddings had a kid table – they probably didn’t trust us to sit by ourselves at a formal occassion. 
It’s funny though, because at the last couple of weddings, we were seated together, and we joked that we were the “kiddy table”, and our parents were the “old people table”.
A nugget is not a finger. Home made chicken fingers can be fantastic.