@Itrymybest84,
Who the hell gets a hotel room (they're not cheap) "just in case" there's an argument? Unless the two of you are separated and keeping up appearances for your son(don't), then that's about the lamest excuse I have ever seen for leaving to meet a paramour.
Because if she was gone over an hour, then that's highly likely to be what she did.
Oh, and she can call any hotel in the US or Canada and probably in much of the world, and ask for late checkout. And if she had no luggage, then she can check out over the phone and even by app in a lot of places.
Her story doesn't pass the sniff test. It doesn't even come close.
So, if I'm right, then she's also accusing you in an effort to deflect attention from her own actions.
As for who is right about your son, I have no idea. I have no kids and don't celebrate Xmas, so the obsession with making those days memorable and perfect and straight out of Currier & Ives or Disney is utterly lost to me.
But I do know that if he's under 18 (and it sounds like he's under 8), then he shouldn't be privy to your problems but you shouldn't deny them, either. If you're an inch from divorce, don't pretend that everything is hunky dory. All that will do is blindside him when you do end your marriage.
Staying together for his sake, if you are, imparts a lesson that love is meaningless and commitment to a spouse is unimportant in the face of lying to a child.
You don't want to be imparting such a lesson to your child.