We’re doing Paris (4 nights) then Bordeaux (3 nights) next September and I keep seeing Biarritz pop up in my research. It’s about 2 hours south of Bordeaux by train. Worth adding 2 nights there or is it more of a quick day trip kind of place?
I’m into surfing (beginner level), my wife loves architecture and markets. We don’t need nightlife. Is September a good time or is the beach season basically over by then?
September in France is usually amazing, so I think the timing sounds perfect. I haven’t been to Biarritz yet myself, but if you enjoy surfing I can totally see why it keeps coming up in your search.
Also for future trips, if you like surf towns with a relaxed atmosphere, you’d probably love Lisbon — or even Datça in Turkey someday 
If you would like a really good detour from Bordeaux in September, assuming you don’t want to do the Pauillac vineyards, how about the Canal du Midi and Carcassone.
