MuFu said:Don't rule out Austria; Salzburg is amazing this time of year. Croatia sounds awesome too (haven't been there myself).
Out of those three I'd choose France - maybe a week in the Alps and a week on the south or east coast.
there are some really interesting things around here (i promise i wont push you to some minefield if you come ).
southern Croatia with Dubrovnik, Pelješac peninsula and islands around there is really great...
Dubrovnik : http://www.dubrovnik.hr/
Korčula :http://www.korculainfo.com/photos/index.htm (birthplace of Marco Polo)
something tastefull : http://www.korcula.net/vina/default.htm
Pelješac : http://www.peljesac.org/index_eng.htm
and its all very close .... with much more around