

SteamOS isn’t quite ready for other devices yet, but you can install something like Bazzite or Zorin as a great alternative to windows. Bazzite is focused on providing an experience very close to SteamOS, and Zorin is extremely easy to learn for people moving from windows to linux. Linux Mint is also a great option.
You can check protonDB for game compatibility, but as a general rule any game or emulation will work fine as long as it isn’t a multiplayer game with particularly invasive anticheat. All Tom Clancy games should work except for Rainbow Six Siege. It uses Battleeye anticheat, which actually supports linux/steam deck fine, but Ubisoft is currently refusing to enable linux support. People are actively requesting support be enabled daily, so maybe Ubisoft will come around.
Might consider this bundle, some of the games are targeted at kids younger than 6, but it’s a good deal for younger players.