That is completely stupid - an evil vampire character would not hesitate to feed on a sleeping kid.
I think Bethesda need to chill out with these pseudo-ethics.
(Slaughter everyone - but please god, not the children!!).
One of the most un-immersive things I have found so far is, playing as a nasty old vampire, being unable to feed on who i want - and that is exactly what a vampire would do.