My six year old daughter's laptop died recently and I replaced it with a small micro PC. I burned isos of 7 or 8 mainstream distro live images on to USB sticks, then let her spend 2 or 3 hours on each of them over a few days, and let her pick her favorite. I even let her use the pre installed Win 11 OS to compare. Fortunately she hated it. She ended up picking KDE Neon, but also liked Pop!OS and Mint Xfce. I think getting to explore around and make her own decisions in the process helped bond her with the computer and the OS in a deeper way than if I had just stuffed something on there.