If you go out of the house, especially with your wife (who is obviously recognizable) then your CDing is not a "closely guarded secret." Your children are young now, but in a few years they will have teenager friends who go out and about and there will be significant risk of your secret being revealed to them. You may not even know when your children find out. My advice, when you have a secret like this, is to prepare the ground by speaking to your children about how we should treat everyone with kindness and understanding, even people who are "different."
I do think you should work harder to find other people to go out with. That's not your wife's responsibility. It's your responsibility to find friends to do this with. There are other CDers in South Africa, I'm sure. Use the internet to find gay bars near you, and then explore the bars to find the ones which are CD-friendly.
That's very well said. For most people, even those who are single, CDing doesn't take over their lives. So married CDers can also probably find a point of equilibrium where they feel comfortable and plateau -- and that can give their wives time to get used to the "new normal" and adjust.