Two quotes from the SDMB:
Triskadecamus:
When teaching your own children, always be honest, and forthright about words, especially words that will get a reaction from a plurality of adults. Children will learn all the synonyms for body parts, and body functions. Some will learn the social consequences of "misuse" of such vocabulary by public embarrassment, but a fortunate few will learn all the names and the social implications of the use of each one from a loving parent. That lesson is somewhat embarrassing to deliver to your kids, but you are the volunteer in this relationship, so suck it up and do your duty.
Weirddave:
Seriously, I think it's important to realize that no matter how forthcoming you might think you are being, how matter of factly you explain that these are just different body parts or how earnestly you explain why the child must use these terms with care, there will still come a time when your 5 year old daughter will pull up her shirt at dinner and say "See my boobies?". Usually this time will be when your parents or grandparents are over.