preschooler vs tiddler

preschooler and tiddler both are nouns.

Word	Noun	Adjective	Verb	Adverb
preschooler	Yes	No	No	No
tiddler	Yes	No	No	No

As nouns, tiddler is a hypernym of preschooler; that is, tiddler is a word with a broader meaning than preschooler:

Other hypernyms of preschooler include child, fry, kid, minor, nestling, nipper, shaver, small fry, tike, tyke, youngster.

preschooler (noun)	tiddler (noun)
a child who attends a preschool or kindergarten	a young person of either sex