Threesome or Not

Most of my life I knew I was attractive to females, had my times of fun especially when my best friend opened up to me that she too was attractive to me. We haven’t done anything in a while and my birthday is coming up I wanted to give my boyfriend of 3 years that experience but now he’s backing down and says that as much as he would love to experience the fun he’s not sure how he would look at me afterwards. He’s not into the whole nine yards (oral and anal etc) Am I’m wrong for continuous bringing up the idea or could I just have my fun with her on the side??