My Angel and my Rainbow

My rainbow is about 4.5 years old now, so I figured he would be old enough to understand about his angel sister. I bought him the book "Someone Came Before You" By: Pat Schwiebert (Someone Came Before You) The book is mostly about a family who had a stillbirth, but since it doesn't come right out and say that, it works for a miscarriage as well. My rainbow keeps telling me that he wants another sister named Kaorie. I keep telling him that in a few years we will look into adopting a little sister for him, since I can't have anymore of my own. 

Since learning about his angel sister, my rainbow has been telling everyone we meet "Baby Kaorie died. Her heart stopped beating when she was in mommy's belly" He has made two women cry and quite a few people very uncomfortable. Talking about babyloss is very uncomfortable for a lot of people, but when a 4 year old tells you something like that it will pretty much stop you in your tracks. I don't want to tell him not to talk about when he feels the need, most of the time he says it, it's completely random. But the looks people give him and the fact that they look like he just cussed at them, I feel like might discourage him. I know that a lot of you will have many different views on this. I feel like I have spent so many years not talking about her, and not including her in our lives that now that my rainbow knows and understands, as much as a 4 year old can, that now is the time to include her in our lives. I know a lot of people will not be comfortable with this and since he is going to full day preschool in the fall, I need to kind of teach him to filter when and where and who he tells about her. I don't need to a call from his teacher telling me he taught the other students that babies die. That's completely up to their parents. I also don't want him to feel ashamed. 

Does raising a Rainbow ever get easy?