Does your husband want you to do it? If he feels it's odd, I would not do it. I would not want to do anything that might make my dh feel alienated from any of our children. Is there a way that your ds and dh could do something during the day together (alone, you know man-stuff), and then you and ds could do something special that evening? I'd really try to bring dh in on the celebration somehow so he does not feel left out and I think it's really important that sons spend bonding time with their dads. And, if you do spend the night in the hotel, remember to book a room with two double beds. :D
Kidding aside, my husband would not spend the night with my daughter in a hotel. It would make him feel uncomfortable. They have lots of what we call "Daddy-daughter" dates where they might run errands together and get ice cream.