a furminator of other kind of undercoat rake if he'll let you brush him will get the dead undercoat out wihtout damaging the top coat.
as others said, DONT shave (by shaving you acutlaly REMOVE the dogs natural protection from the sun and heat)
id buy a real cheap kiddy pool (check out freecycle.com for your local chapter than put out a wanted add for a couple free ones. (that way if he destroys them, no big loss for you)
a sprinkler, or hose would also work if you cant/dont want to go the kiddie pool route. a big beach unmberella over the pool will create a shady place to play. just make sure you understand itll getmuddy with all the running round and udmp out the pool every day to avoid it being used as a mosquitoe breding ground
some other fun games mydogs liek when its hot are anything involving icecubes. toss a hand full of icecubes in the kiddie pool or his drinking water to play bobbin for icecubes, or let him chase one across a tile/hardwood floor.
my frandfather used to fill an big ole bucket with water, and toss in a veriety of rubber dog toys, then put it in his chest freezer. once completly frozen hed toss it in the large kiddie pool he had for his saffy who would play with it in the water and as it melted toys would be freed so the game was endless, he would also do "ice pops" for the chis, in an icecube tray hes take natural none sweetend yoghurt, and organic (pesticide free) blueberries blend into essentially a smoothie and spread it into the icecube tray. the dogs LOVED them. you could also use chicken/beef broth.