I don't know about Bordeaux but I live in San Sebastián and have a toddler and it's a brilliant place for him. He loves the aquarium. The carousel on the beach front and the pintxos (perfect toddler size!) the beach has a climbing frame and there's a little amusement park at the top of a mountain that we take the funicular up to.
Obviously we prefer it to France and are biased, but I find northern Spain much more toddler friendly.
Le petit train de la rhune on the border is worth a visit if you have a car, it's a gorgeous train that goes slowly up a Pyrenee with incredible views.
Hondarribia/fuenterribie is gorgeous but not much for toddlers to do there.
Biarritz is very nice, I like buying his clothes there 
One of the best places in France for him in the summer is Les Landes just between Bordeaux and Biarritz. Miles of beaches and campsites with quite quaint little activities, a little zoo,
A forest full of monkeys and lots of little swimming pool type places.
The Spain side of the border, San Sebastián is the best place around, Loyola is interesting for a day trip, pasaia, the fort in errenteria or even
Bilbao for the Guggenheim.
Hope that helps!