Jeff,
Since you asked, my two Eurocents, for what they're worth.
There are only a few make it-break it conditions which a couple has to mutually be 100% in agreement on in their relationship.
1) How to deal with the mother-in-laws. It may be 2009 and we may all laugh about how str8s marry their mommies, but fifty years on this earth have shown me, a man's a man fo' aw of that...
2) You have a firm rule on sex outside of your relationship. I don't think it matters so much what the rule is as that there is one and you both adhere to it utterly.
The worst situation of all, in my experience, is when a gay man takes a bi-sexual as his partner. Never seen that one cause anything but disaster - for the gay man.
The next worse is the situation I found my self in not once, but twice - HE can (and frequently does) but YOU are to be chaste as the temple virgin...while he is out giving Messalina a run for her money. Number one insisted we have an open relationship. By that he meant, I was to be open to his playing around. Number two was insanely jealous, questioned my every move...and while I was NOT sitting under the apple tree with anyone else, he was gathering flowers where 'er he might...
Personally, I am monogamous and can't see my life any other way. Now that we have hard statistical data that, in fact, roughtly 17% of all men (gay and str8) are built this way, we no longer have to put up with the bullshit which was dumped on us by so much of the gay community for so long. It's how we're built. Time to end the moral judgments on both sides. Is you is or is you ain't...once you know, choose your partner accordingly.
The pain it would cause my partner (who is also built monogamous) far exceeds any pleasure I might get. Or worse, be giving. But, again, I'm built that way.
So, my advice to you - stick to the rules you two have. Twenty-two years together means you must be doing a lot right. Personally, from the sound of it, you two need to discuss the rules again and maybe either make some changes (I've been in long term relationships where the sex was still great after 15 years) or maybe not.
Whatever, busy little bees that we are, we're always happy to tell you what to do (and no fear, the queens who take notes to narc to the FBI and people's employers are, this instant minute figuring out how to let your partner know everything...)
But the guy you really need to be asking is your partner. Maybe he will say "Oh, her, been there, done that". Have fun, be sure to wear condoms, you won't need lube, maybe just a rope to find your way out again.
Or he might offer a ménage à trois.
Or he might rethink why you two aren't having fun in bed.
But he won't throw away your life and love for talking to him.
He knows what's up at some level, anyway -
Good luck, Jeff, whatever you do. It is nice to have a young guy look at you and see him drool. Of course, while you're thinking firm young thighs to plunge into, he may be thinking, "Daddy!". Er, um, ick.