Put on some Loony Toons! Don't worry that it's old. Kids that young don't have enough sense of the timeline to know just how ancient any animation style is, but Loony Toons will stand out for sure. 3D garbage-tier animation is everywhere in kids shows because it's fast and cheap. 3D animation is often much less expressive and dynamic though. The more variety in animation you expose a kid too, the sooner they'll be able to notice bad animation when they see it.