Here are some of the things I took away from your post:
You think people don't know you're gay, but they probably do.
Being gay/bi is still a very taboo topic to raise, especially when one's not out, and in probably 90%+ of the coming out stories people tell around here and on other websites, almost always the confidant says, "I always sort of suspected but didn't want to say anything," or something of that nature.
So while you say family and friends would be devastated if they found out, don't think they don't suspect already, because often times when people get the "vibe," they will fervently try to ignore their feelings as a way to respect you better. (It's odd, but true, although it can also be the complete opposite. One of my friends claims to be straight, but I'm 99% convinced he's gay, so whenever he raises gay topics (which he does quite frequently), I make suggestions like, "oh please just come out already it's no big deal, I did it!")
Divorce is common; don't worry about losing your kids
People get divorced for a variety of reasons, and I would argue this might be one of the most honorable reasons.
Think of the alternatives: infidelity, abuse of finances, drug/alcohol problems, physical/mental abuse, etc. That you kept something bottled up to protect your family, and that coming out when you were in your 20s wasn't as accepted as it may be today, isn't nearly as bad as the other options.
You are still the father of your children, you've provided for them throughout the years, and no judge will take them away from you.
Grow a pair, and tell your wife
She's looking at other men for a reason; whether she suspects you're gay, or wants dick from another place, she's unhappy.
I got the sense you're hoping she does find somebody, so you can then get divorced, and the reason for said divorce won't be that you're gay, rather she cheated, and you can continue hiding from the truth.
It's time to man up. Sit her down and tell her you love her, you love the family you've created together, but you like dick.