toddler

babe, baby, bantling, infant, neonate, nestling, newborn, tot, tyke (also tike), weanling

bairn [chiefly Scottish], bambino, bud, chap [Southern & Midland], chick, child, cub, juvenile, kid, kiddie (also kiddy), kiddo, moppet, sprat, sprout, squirt, whelp, youngling, youngster, youth

adolescent, minor

kindergartner (also kindergartener), preschooler, rug rat [slang], schoolboy, schoolchild, schoolgirl, schoolkid

brat, imp, jackanapes, mischief, monkey, rapscallion, rascal, rogue, urchin, whippersnapper

cherub

preteen, preteen-ager, subteen, teen, teenager, teener, teenybopper, tween

lad, nipper, shaver, stripling, tad

bobby-soxer, hoyden, tomboy