My DD is only 21 months. We say vulva. I may also teach her yoni when she gets older, more for a comfortable term to use with her friends as she hit puberty. I had never heard to term yoni until I a couple of years ago, and I was raised by an earth mother type, who taught me to say vagina. I definitely plan to teach her all of the parts of her genitals as it comes up.
Although I have identified her anus on many occasions, I generally say heiny. It's the term my mother used when I was little. I think it's cute. I talk about her cute little heiny. I tell her that she has poo poo on her heiny so I need to clean it off, etc. Yesterday her 3 year old cousin showed her how to strip one of her babies that happens to be an anatomically correct boy. She pointed to his little penis and said heiny
I told her that it was actually his penis, which she repeated. We have identified daddy's penis before that. I'm trying to use vulva more often so that she doesn't just call the whole area heiny.