Hi Lisa--
Congratulations on this terrific opportunity. I'll throw in my 2 cents on your questions. . . but I'm very interested to hear what thoughts others may have as well! I like the amount of shoulders you're showing, I like the vignette concept. . . but the fairly sharp solid 'fade' at the lower margins conveys a 'floating' sense to me. Vignettes that sort of dissolve to lines that fade better convey a sense that the body continues. Not sure if I'm expressing that well, but Marvin's 'Samantha' would be an example.
You didn't say whether these portraits would be going to different homes (being given to the award recipients) or hanging as a group. If they're going to different homes I'd say definitely treat them independently, color wise, etc. I'm thinking that'd be more interesting for the whole group hanging together, as well, and make them more visually interesting to look at. Assuming the scale and size of the portraits is consistent, your style will tie them together anyway.
As far as getting approval from the individual women, I think that'd probably be a good idea (if you can manage it in that time frame!) Especially as it sounds like some of these images might be shown in the press and if the women are more mature as the one your showing, they may have features they'd rather have de-emphasized. For instance, on the woman above, you might de-emphasize some of the wrinkles just above and below her mouth... and maybe soften the folds on her neck? without loosing a sense of her age. . . and she might more like to see herself portrayed that way? (I will admit, I'm in the flatter your subject camp most of the time
)
Anyway... This is beautiful!
Good Luck!