Quite an interesting idea....
Let's see.
For Lilly: elegant, refined, sweet.... kinda plain, but in the good way: gotta' be good old French Vanilla.
For Hanako: Subtle, equally sweet, bit of acquired likeness: probably Licorice or something like that.
For Shizune: Semi inviting, slightly sour at first, but pleasant aftertaste: I agree with Blue Raspberry. Gotta' be.
For Emi: Got that kicking feeling (forgive the pun. xD), peppy, hot-headed sometimes... COFFEE. At least a Mocha.
For Rin: Deep and Rich, yet strange and unpredictable... ooh that's a tough one. I would LIKE to say somekind of red wine, but Rin's just not that high class. xD EDIT: OH! I just got it... ROCKY ROAD!
Kenji is hot sauce mixed with vinegar. LOL.