As long as he's not looking at really creepy stuff, it's all good. And by creepy, I mean anything involving feces, animals, Germans, or any combination there of.
Why not just give the kid a gift card to some online sex toy website, and then he can just order it to the house and mom doesn't have to worry herself wondering what's in the discreetly wrapped brown box that arrived in the mail?
My Mom rented us (2 daughters, 1 son) porn every now and then, when we'd ask for it. There was no internet back then, see. She let us swear at will once we'd demonstrated we knew how to self-censor appropriately. We went to nudist camps a few times for a few summers. She showed us that if you treated people's nudity or sexual interests or other vices with respect, they should return the favor by respecting your ideas of what was appropriate. I would teach it to my kids in a second, but I didn't have any. One thing I never grew up with? Shame over sexual feelings. From what I read from other people, I dodged a hell of a bullet. Thanks Mom.
And "mother gives her 15-year-old son a dildo after catching him surfing hard-core porn at grandma's one too many times" ain't it.