You and I seem to have similar backgrounds - prep school, Ivy League, professional. But - I am always taking my little girls (ages 4 and 7) to the nail salon with me. In fact, we have mani-pedi appointments after they get out of school today!
Don't get me wrong, I am pretty conservative when it comes to parenting. I do not allow them to watch SpongeBob or Hannah Montana, they don't wear skirts or shorts above their knees, and I wouldn't allow them to wear anything that showed off any midriff (except bathing suits, but, well, they're bathing suits).
But I just don't see what the big deal is with nail polish. It's not sexual or grown-up. They typically choose colors that no adult would ever choose (teal blue sparkles last time). To me, the salon is sort of like the Mother Ship. Any woman with decent grooming habits will end up spending a good deal of time there throughout her life. Why would I want my daughters to grow up with ragged cuticles, bitten-off nails, and then at some point (13? 16?) expect them to suddenly care about the appearance of their hands? I think hair care, skin care and nail care are best learned from the cradle. But that's just me! =)
As an aside, I do think that there tends to be a fair amount of prejudice against the "girly-girl" on Ivy campuses, as if being beautiful and being smart can't possibly coexist in the same person. Being beautiful DOES get you farther in life. Study after study shows it. Sure, the Dartmouth degree moves my resume to the top of the pile, but being pretty and well-groomed gives me an advantage in the interview over those with similar educational and professional backgrounds. It is what it is, and teaching our daughters that beauty/grooming doesn't matter does them a disservice. Again, just my opinion, and I look forward to reading what other Mamas have to say!