Bluetooth or lightning headphones (Lacey - Hawks prairie)

Hello. I am looking for bluetooth headphones for my grandnephew. He likes to listen to things on this the old iphone. The one that only has the lightning headphone jack, but we don't have a bluetooth or the lightning headphones. But what I do want is a way that he can listen to the things he is allowed to listen to, but not my kids, because my kids are younger and the content is not for them. I would appreciate any help. even if you have a lightning plugin headphone.