Your dog's should be fine with the breaks you have planned, providing they are not too big for your car. I regularly travel from the UK from Portsmouth to Caen, and drive right down to the South of France with my 2 dogs, both Jack Russels. I take regular breaks, and always carry water for them. I tend to take a couple of days to get down and the same back, usually camping on route (going different ways each way) I keep the air con on in the car at all times in summer, and usually let them have a swim in a river or too, though this does give the car a distinctive aroma!