chakman,
Noddy gives excellent advice.
Your clues about having 'only been' with your hubby because you were childhood sweethearts is wonderful and, well, sweet. If you are truly happy with your husband, please shun the 'call of the wild'. Its lure is likely not as desirable as you might think it is.
Yeah, you might have an evening of hot, ferocious sex--but what about the fallout? What about your commitment to your husband? Your marriage? Your children?
And, just as likely, that 48 year old guy is likely just looking for a little fantasy too, nothing like a committment.
If this helps, it isn't at all uncommon for women of our age to indulge in fantasies about being with other men even in the happiest of marriages. But that's what it is--fantasy.
You said your sex life with your husband was 'great' but perhaps something is lacking. LesVal suggested a little role-playing which never hurts and can be great fun.
Realize that your attraction to the other man isn't really about him at all. It's all about you.
Now what you do with that knowledge is up to you.
Don't blow off a good life. Redefine your focus and have a little more fun at home.
Good luck.