So sorry to hear your news. It's entirely upto you if you want to tell others or not. My dh and I had decided that we will not tell anyone if we went down the donor route. I just could not trust family or friends with our secret.
So sorry for the news sounds like you have accepted the donor sperm route. I would tell your friends what you want others to know because friends talk. To others. So i would say be wise with who you choose to tell. Otherwise just tell them everything is all set to go so treatment starts in April. They don't have to know the details; just you are good to go.