Well, lets take a look at how the 16-year-olds who got to use ChatGPT ten years ago have turned out...
In seriousness, as others have been pointing out, the big online AI assistants are all super neutered these days. I think it's probably fine, and indeed given how these tools are going to likely become more widespread in the future I think it's a good idea for kids to get used to using them. At 16 I'd say they're too old to sit them down and give them a lecture about "it's not really aware, it doesn't feel emotions or have memories, and if you go to it with any sort of medical questions definitely double-check those with another source" - lectures at that age are probably going to backfire from what I've seen. Instead, suggest that they research those things themselves. Just put those questions out there and hopefully it'll motivate them to be curious.