First, never let your pup play with the bumpers. They are yours, not his.
Some puppies are crazy to retrieve from day one, some are not.
I like to take young puppies for walks where they can explore everything they are curious about (which is everything). This gets them used to the surroundings, builds confidence and at the same time builds the bond with you. You are the safe place they return to when the pup sees or smells anything intimidating.
I take a bumper or the pups favorite toy along and surprise the pup with a "hey hey" and toss the toy for him to retrieve. Just once or twice at first and not a big deal if he doesn't bring it to you. Make those one or two retrieves the highlight of the pups day. Gradually increase the number but always leave him wanting more. If he has it in him, it a few weeks he will be going nuts wanting you to keep throwing.