To all the famous wine regions near Bordeaux you can book day trips at the tourist office, where they have a special counter for these trips. You can find tourist information at the corner next to the Quinconces square (where the Girondins fountain is).
The castles are beautiful as wel is the countryside!
Château Ausone

Chaâteau Dufort-Vivens

Château Labegorce

Château Malescot-St. Exuperie

Château Margaux

Château Palmer

Château Rauzan-Segla

Château Sénéjac (where I lived, years ago)