Is normal

A couple months ago my wife went to a local nite club with some girl friends. She is over 40 and actractive. When she came home she told me that she had a great time but she was feeling guilty because she had danced very eroticly with some other men. She was doing some grinding and allowing them to touch her gently. At the end of the evening she came home and was very excited and told me what she had done. She was not sure how I would feel about it. We had great sex that night and I found that I was turned on by her story. After discussing this some more with her we are now going to clubs together so I can watch her flirt and dance with other men. This is as far as we are interested in going, just some teasing, light touching... We have been married over 20 years and have found this to really spice up our sex lives. I would like to see comments from other married/nonmarried couples. Is this normal?