I did something similar fairly recently as my Roku TCL kept getting worse. I had a NUC only running PiHole. I mainly use Plex with occasional YouTube via GrayJay so your use case may be different.
I tried LibreElec, but it kept hard crashing - maybe a video issue? And getting Pihole running on it was a pain.
I jumped to KDE Neon Big Screen, but Plex HTPC ran like a slideshow at 4k. Everything else ran fine but I didn't spend much time troubleshooting.
I next tried Mint and got it working just fine. Plex, Grayjay, Pihole, and a cheap wireless remote with a keyboard on the back. I set the desktop scale to 200-300%, hid the taskbar, and put a couple huge icons on the desktop. It's not perfect, but it's simple enough for the kids to figure out.