Congratulations bud. I'm currently counselling two different friends in healthy marriages with multiple children about how to deal with their orientation.
Both value the relationships, one has come out, and is still struggling to figure out what to do. The other has no plans to come out at all, fulfills a few physical urges when out of town on business, and feels very guilty about his "problem", and wishes it would just go away.
The kids were surprisingly supportive - I think that they still see a dad, and it is what it is.
My position has always been to do what feels most comfortable for you - but I firmly believe that openness leads to less stress, and if it is correct for the marriage to end then so be it.
Physically, if you're sexually active outside of the marriage, you have a responsibility for her health, or at least in letting her know that she needs to be concerned about it, the same way you would in a non-exclusive gay relationship, and there are plenty of threads here that discuss how these work.
Congratulations - and good luck getting a modern family to work.
