Some of one's children's items – a couple recent, a couple less so – all written with a particular grandchild in mind and each written with the notion of it being read aloud to them, so explaining the use of a word or two that may seem beyond the item's apparent age range. But meeting new words is part of a child's learning and growing, so I've never shied away from doing it. As a rough guide, "…Billy Boiglebird" and "Raggedydax" are for 5 to 10's or so, "The Enchanted Music Box" 7 to 12 perhaps and "The Fat Frog Song" is for the littlies.
As for "Grandma And Me, And Bernard, My Elephant"... well, that's specially for kids aged between two and eleventy.