Natasha,
I don't know if I agree that it's a generation gap thing. My wife's family has quite a generational spread (oldest nearly 100, youngest just a few months), and half of it comes from the capital and half from the countryside (Duverge, Independencia province). They ALL ask for the blessing, although it's true that some of the younger ones are not so demonstrative about it, especially when their friends are around. I was always told that if you were "raised correctly" (i.e., polite, well-mannered), the blessing is asked of all parents, grandparents, godparents, aunts and uncles when you first see them. My wife certainly always does. I picked up the habit. I notice it immensely pleases my suegra and tias every time I do it, but it freaked out my tios (still not clear why, although my wife explained it once), so I stopped doing it to them. Our kids, which you know are fully bicultural/bilingual, have picked up the habit and I must admit that I kinda like it when they come every night and say "bendicion Papi" and I reply "Que Dios te bengida, mi amor!"
Regards,
Keith