I didn't know I was having a C-Section & so I just took what you normally would. (even Bonds hipster undies) I didn't have any extra needs except for clothes for the extra days in hospital, just a little advice on the sizes of your clothes you plan to wear afterwards:
Take some maternity clothes, I expected my stomach to be gone immediately & it didn't happen that way. So make sure you take clothes that you wore perhaps when you were 20wks or less. Just give yourself extra room and people won't notice too much if your stomach remains a little bigger for a few days.
Good luck with your op & recovery! I had a great recovery (check out Positive C-Section stories forum for all the datails!)
Hope all goes well for you, bubs & partner!
CJ, SJ 3/03, AJ 11/05, PJ 4/08