I use correct terminology because of all the reasons listed above.

I also used to find it a bit "giggly" saying vagina and penis, and I was very concerned about this embarrassment passing onty my child in a negative way - after all, to them it's just a body part, I didn't want to stigmatise their body parts. So - and I kids you not - I stood infront of a mirror and said the words until I was comfortable with them It might sounds REALLY silly, but it worked