Change your expectations. You are expecting him to show he's having a good time. Just because he doesn't show doesn't mean he's not having a good time.
Look at the positive. He had a good time. That means he'll want to spend more weekends with you. This is what you want.
You want better reactions out of him, but that takes time. Keep him wanting to spend time with you, and he'll start to show he's having a good time, and then you'll have it all!! If you had to pick one, which would you choose? Him faking he's having a good time, or him having a good time but looking grumpy?
BTW, one big corner I turned was when I stopped getting bothered by my X's antics, and starting laughing at them. When she could no longer get under my skin, she was easier for me to deal with.
