I have an 8 year old who is very excited and a 10 year old who is also very excited but I’m pretty sure she knows what’s going on but is playing along for her sister. They only get one present from Santa and the rest are from us so the Santa present is the big one they asked him for. I now have a two year old nephew who is so excited you could use him to power a reactor.
I guess there will be a small gap where no one belives in santa, then it will be a good time to go on holiday for Xmas, and everyone will still be excited for Xmas.