Hopefully you can find some minor comfort in these words.
I came out as MTF to my wife a few months ago. At first she was all over the place, fear, sadness, anger, etc... She has calmed down though and we are moving through this process fairly well.
When I first discovered I was trans, my mind immediately jumped to all the things I wished I could do, wished I'd done, and hoped to actually do! Many of those things included going out to bars, meeting other men/women, and all sorts of things ran through my head, BUT! As the days turned into weeks and the weeks into months, and I eventually ended up on hormones, I realized that it was just fantasies created by my maleness. Stupid maleness! It made my wife feel terrible for no good reason!
Now, all I want to do is just meet people, be accepted, be their friend, and be happy being me. While looking FABULOUS doing it, hehehe. I feel sure that he will feel the same way and these notions of "spreading his seed" or whatever you want to call it will calm down, but it will take some time.
This is just my opinion and my own experiences, YMMV, but hang in there dear, for a little while longer at least to see!