Kitty Kat?
I still think “snatch” is a decent term…
Is ‘penis’ that general of a term??
How about crotch, for the generic? I also like ‘privates’ - I’ll probably use that one, I like the sense that they are personally owned and private. For most ‘I got hit with a ball’ kinds of comments, gender-specific is not the point. Localization of injury is the point, and the teachers know the difference between boys and girls without being told.
For the gender-specific, my mom used labia. She tried saying vulva, but I found the term still too general. When I was talking about my parts at that age, I usually was talking labia - the rest was pretty inactive until much later. Heck, I even knew labia majora and labia minora, as terms.
My son knows ‘penis’ because that is the part he plays with, and the part he has to remember to point the right way when he pees. Girls have less active interaction with their exernal parts, so there are fewer reasons to name specifics on a regular basis. But I still prefer accuracy when specifics come up.
I vote to leave vagina in the ‘where babies come from’ conversations, at this age. My mom tried to explain to my 3-yr-old son that his (female) cousin would not develop a penis when she grew up (no matter how much he thought she should), just as he wouldn’t develop a vagina. Unfortunately, the vagina is such a hidden part, that he was totally confused. Of course, mom wouldn’t show him where it was, and had a hard time explaining the placement… How magical, hidden parts! So he kept saying he had one, too (Mommy, I have a bagina on my bottom!). I finally cleared it up by explaining that girls (women) had a special place in their tummies (called a uterus) just for growing babies in, and the vagina is the place the baby comes out. And only girls had those parts, and only boys had penises and testicles. (complete with references to mommy and daddy) Once it was in ‘grownups and babies’ land, instead of in ‘my parts are cooler than your parts’ land, he was fine. He got the “Oh, NOW I understand” look on his face, which is priceless.
I wish we had discussed the ‘what we call the parts’ thing with my mom before now, though. At least I remembered to warn the babysitter. What fun having same-age, different-sex cousins both potty training at the same time (and often in the same house, and often half-naked). Whee.
Oh, and I also like 'nads instead of testicles (or ovaries, for that matter). Short for gonads.
When I went through training at the local rape crisis center, they told us that, in dealing with little kids, one term commonly used is “front-butt”. I’d never heard that one before, but it makes sense, in a strange way…
Hmm… How about “cunny”?
Well you’ve given him his direction in life haven’t you? 
I have a deeply religious cousin who’s nickname for her daughter is Cunny. She and her husband honestly do not have a clue as to the slang connotation, and no one in the family (and apparently none of her friends),including myself, have the muster to explain it to her.
The child in question is now 11, and for several years has been an exceptionally good figure skater who travels quite a bit to compete. Her parents travel with her, and are always front and centre in the crowd on their feet cheering “Go Cunny! Go Cunny!” The home club crowd is used to it, and thinks nothing of it, but some of the looks on the faces of visiting parents and out of town crowds are quite remarkable. Frequently my cousin and her hubby will remark that they are concened that so may parents take the sport so seriously that they are offended over parental cheering. When they say this, it’s all I can do to not break down laughing. The best is when her grandfather (my uncle) named Nobby comes to town. People in the stands overhear things like: “Nobby, go down and get Cunny.”
Fortuntely, they are terrific parents, and the child is truly wonderful. I expect that whever the child learns how some folks perceive her name, she’ll probably just think that those folks are wierd.
I’m just glad my folks called me Muffin. Given some of the names in my family, it could have been a lot worse.
I try not to say “tods” in front of the kids. It might upset their mothers if they repeat it at home.