I think this is a really important question, and I wonder about it myself. My daughter was conceived during my rape, so that makes my situation a bit different. I think that when the time comes I will tell my daughter as well as my other children (not at the same time). I want them to understand that rape happens, and to people they know. Rape jokes are not funny, no means no, etc. I hope that they will become advocates against rape culture.
I have always been very open with my children (age appropriately of course) so I think it will feel congruent with our relationship. We aren't a family to have "family secrets". My parents do not know, however, and I will wait to tell my kids until they can understand that it is my choice and they need to respect it.
and congratulations on your new baby!
I haven't been raped, but I think that I would share this with my children when they were old enough to know. That age is different for each kid, so there isn't a "magic age" but I can't imagine keeping it buried. However, I wouldn't ever criticize someone for keeping it to themselves. That is a very personal decision. I think as your children grow, you will know more about what would be right for you.
I haven't been raped but I supported a friend through this many years ago. It's something that stays with you. :-(
I really think it would be good to talk with your kids about it when they are at the age of starting to develop dating relationships. Your son might someday speak up against his friends or educate them based on what you have told him. I was raised in an abusive home for part of my childhood. I have shared that with my girls, and told them how that is wrong and no one should ever treat anyone that way, for any reason. I think knowing about my struggles has made them stronger, wiser people. Now they know that is wrong and will hopefully avoid that kind of relationship.