Hi, suggest you use viamichelin as your primary map routing.
Suggested route, avoiding Paris is as per this link . Can't speak for the Calais to Bordeaux section as we always use Caen Ferryport then Rennes, Nantes, Bordeaux. The whole trip is doable comfortably in 2 long days...especially in April when the long winter nights have all but finished.
There are a couple of dog friendly hotels to the North of Madrid I would suggest that you check other threads on htis forum as this subject has been covered many times. Try searching under the subject 'Driving to Spain'
Legally remember you will need to bring with you your Vehicle Reg documents, proof of Insurance, MOT cert if applicable, High Vis Vests for driver and all passengers, a spare bulb set (and the tools to change them), 2 warning triangles, and if you wear glasses for driving a spare pair. European Breakdown Recovery Insurance is also a good idea...
Hope this helps..
fb.