To be honest this doesn't seem hard to decide or understand.
Youtube gives you a binary decision, whether to tell that your content is targeted for kids or not, "targeted" being the keyword here.
Not "appealing" to them, actually "targeted", "meant" for them.
Because when you set it being for kids, it is assumed that your target audience are kids, and kids only.
If all you have is UT videos and techy stuff for example (didn't check, just assuming), then your content is clearly NOT for kids, so just set it as such.
Legally speaking, NOT for kids is a much safer choice when it doubt than stating that your content is for kids, because all you're saying is that your target audience aren't kids.
I mean, imagine that you had videos with nudity in them, they're certainly "appealing" to kids, especially the ones hitting puberty, but they're certainly not the targeted audience, and you saying that those kinds of videos are meant for them may get you in more trouble than if you just set them otherwise.
From there, whether kids see it or comment on your videos, it's Youtube's problem, not yours, since you have already clearly set that kids aren't your target audience.
Many kids will just create accounts where they portray themselves being older than they actually are, if they haven't already.
If you're not even monetizing anything, you have even less reason to worry about.
So relax.

And if it wasn't clear already, I have already set my own channel to NOT for kids as well, and I have UT99 videos there, as well Fortnite videos (Fortnite being popular mostly among kids, but they're not my target audience).