Prom :(

I have a dilemna. So this guy from my work likes me, and I don't like him. He's nice and all but I don't think we are that compatible and he is in high school. I do not want to date a person in high school. Before I knew he liked me, he asked me to prom, and I am too nice of a person to say no. Also I don't think I am ready to date anyone, and if I did, it would disrupt the homestasis of the relationship. I will still go, and have a good time, but I don't want to give them the idea that I am interested beyond friends. Hopefully everything will work out.