I hate running into things like this. It truly is a reminder that I was married to a complete stranger and didn't know it.
The thing is.... he was a bad person. He lied to you, he cheated on you, he broke the most sacred vow a man can make. So is it really surprising that he would misuse a corporate account to finance his playtime? No.
I keep learning new (and shitty) things that my EWH has done. I've learned he's an equal opportunity deceiver. No one, including OW, has been left out of his lies. Sometimes I almost feel sorry for her. She knew he was a liar and a cheater, obviously, but I think she seriously has NO CLUE what she has gotten herself in for.
Anyway, I know this hotel thing seems really important, but its not. Try to view it (and other things you may discover over time) as validation that this guy is a complete dirtbag, dishonest in every way, and you are well rid of him.
My advice is to book an amazing get-away with your kiddos, and stay at any other hotel chain except that one. Have a wonderful trip and don't waste a moment of it thinking about him!! Me: Enjoying life
Him: Someone else's problem
Life shrinks or expands in proportion to one's courage. ~ Anais Nin