Obviously if you don’t know what he likes it hard
Lego, could be sold on with little to no loss. Star Wars and Minecraft definitely not too young for this age.
If parents are gamers then I would definitely assume he is. Roblox is popular at this age, but again if parents are gamers he may well be into more “advanced” games. My 8yo DD loves Roblox but will occasionally play Fortnite with DH and 10yo DD. Never liked Minecraft but my older DD did.
My 10yo DD has asked for Mario Cart for her switch, also very popular and they also have Mario Lego which is also popular.
I can’t see gamers having an issue with nerf guns given how many games involve killing and shooting.
Is there any way you could find out if they have gaming consoles? You can also buy V bucks, which is money to spend on PlayStation games.
Safe bet for me would be clothes to be honest, next size up in case he’s big for his age and go with something popular, Roblox, Minecraft or any gaming type hoodie or Oodie, or Nike, Adidas branded clothes. Sports Direct vouchers may work?
Id also include a gift exchange receipt.
Will the gift even be accepted given it sounds like there is little relationship there? I refused gifts sent to my DDs from estranged grandmother.