As always, Pit has good advice. you need to be ready to house the snakes properly as soon as they get home. Don't make the mistake so many make by purchasing an animal you are not ready to care for, no matter how exciting it may be. don't get suckered into buying some silly exo-terra or similar set up. your new snakes will almost certainly be hatchlings and will do fine in small tubs. you may even consider purchasing the snakes and have the breeder hold them for later delivery/pickup while you get set up.
Unfortunately, only Mother Nature can create new morphs. it's unlikely, but remotely possible, she will utilize your son's snakes for her next experiment. even the likelihood of creating a "world's first" combo is slim unless you are buying rare/high end morphs. Don't set the bar too high and I'm sure your son and you will not be disappointed.