Caroline is DEFINITELY an ENFJ, I identify with her too much. Her cute comments and ability to notice subtext just doesn't make her an S to me. She's very intuitive. Plus, I think if she were an ESFJ she would be more like Elena.
As for the others:
Elena: ESFJ (although I do think that her S and N are close). She's more S though since she doesn't really understand her feelings for Damon. It makes sense she would be "The Caregiver" too.
Stefan: INFJ - He wants to protect people, especially Elena.
Damon: ENFP (I think his F is messed up from what Katherine did to him, since he used to be super kind and giving. I also think his N/S are super close).
Bonnie: ISFJ (she cares too much to have objective control over her magic)
Alaric: INFP (he cared too much about his wife before to be a T)
Katherine: ENTJ <-- LOVE HER!
Tyler: ESTP (still a bit uncertain about this though)
Rebekah: ESFP (but tortured!)
ALSO* I think Elena as a vampire will develop more of her N, especially once she accepts her feelings for Damon