I have another dog who can't handle excitement in the heat. The only trips she ever gets to go on is to the vet and back.
But, something to consider is getting a cooling mat. They have them at Petsmart and Petco. You just fill it with cold water for the puppy to lay on. It cools them down physically, and helps them to calm down, and not be so excited. You could even use it in the car.
Good luck.