My little one just past toddlerhood has a few games they love to watch me play on my Steam Deck. These aren't all Verified, but they all run perfectly out of the box. Use ProtonDB for a more accurate idea of a game's Deck compatibility (Verified status has failed me in the past).

• Donut County (already mentioned, but a great one worth mentioning twice)

• Everything (one you unlock all the powers, it becomes a sandbox game where you can do things like gather a large group of caterpillars, make them dance, and turn them into streetlights (which can still dance), or turn an entire planet into a planet-sized space caterpillar, or turn a dust mite into a microscopic building, etc. In my save, about 20% of all matter in the universe is caterpillars.)

• LEGO Worlds (basically LEGO Minecraft with less survival, more control, and smaller worlds that can be swapped between at any time. Can be very fun for little ones to use the free DLC vehicles to blast holes all over a world, make tunnels, etc.)

• Tchia (Zelda BotW mechanics with very little combat (and the only combat is with enchanted scraps of cloth) and the ability to jump into and control any creature (dolphins, birds, cats). It's got some nice family-friendly options, like infinite special meter, no death, and family mode for cutscenes (though there isn't anything too bad, regardless))

• Webbed (a 2D platformer where you play as a spider with Spider-Man-esque movement. Fun for kids unafraid of spiders to make big, climbable webs, and maybe good to help kids become less afraid of spiders, as it's pretty cute)