Hi Anita,
Welcome. I am brand new here myself, and I certainly do not have the insight that those already advising you here have, so their advice is best. I am a straight male with 4 grown daughters who is trying to learn more about TS MTF women. I am already separated myself. My main question is whether you have grown children? You are my age and so you are old enough to have grown children. I am very close to my daughters and so if I had such a serious issue to deal with I would probably broach the issue with the most mature of them privately and ask her what she thinks I should say to the rest of the family. Children love you unconditionally, and I believe in my case at least that there is nothing I could reveal to them which would alienate them from me (barring serial killer, etc.). That is just me, and it might not be the best thing for you to try. I do not mean by this that children should be involved in the dynamics of such an issue at all, but their insight, loving both parents, may be valuable, taken as advice to contemplate. If those on this site believe that this is a bad idea based on their own experience, then I would defer to them. At any rate I truly hope all works out as best as is possible for you and your spouse.
Sincerely,
Dan