Kid sims age out of the base game fast. Toddlers get a handful of outfits and about four hairstyles, children get hand-me-down meshes that look like shrunken adult clothes, and infants — added years after launch — got almost nothing at all. So the moment you play a household with children in it, the kids are the ones who look unfinished while the adults look great.
This collection is every kid find in our catalog in one grid: 686 mods across all three young ages, sorted by downloads. Toddlers are the deepest shelf by a wide margin (362), children next (266), and infants the thinnest (81) for the obvious reason — that age is the newest and creators are still catching up. Hair is the single biggest category here at 164 sets, which tracks: it is the slot with the worst base-game coverage and the one people notice first. After that it is everyday clothing (92 full outfits, 61 tops, 31 dresses, 17 bottoms), 46 pairs of shoes, 58 furniture pieces, and 59 pose packs — the poses being mostly family and sibling shots, which is what people actually photograph kids for.
A few creators basically live in this category. casteru has the largest single shelf (toddler swimwear, formalwear and CAS poses), PowLuna makes matched toddler outfit sets, RavenSim and Lewbertsn00tles do the hair — including child and infant conversions of hairs you already have for adults — Flystone covers child shoes, and Madlen and Talarian fill in the school-uniform-and-tee end of the wardrobe.
Two things worth knowing before you download. Ages are separate meshes in this game, so a set made for children is not automatically available to toddlers, and a lot of the packs here say so in the title ("Child and Toddler") precisely because converting takes extra work. And infant CC needs the infant update installed; if a download looks empty in CAS, check the age it was actually built for before assuming the file is broken.
Everything in this grid is Sims 4 only, filtered to SFW, and checked for a working download link — 562 of the 686 are free. Sort by downloads for the sets most households already run, or scroll for the single releases the big roundups skip.