Avoid the Death Route! 

Isekai de Mofumofu Nadenade Suru Tame ni Ganbattemasu 
-note: manga is cuter. 

FEEL FREE TO ADD YOUR SUGGESTIONS HERE.

There were also quite a few Otome Game Villlainess novels where the MCs spend a good amount of time in their cute childhood; unfortunately, I can't remember which ones. 

OMG, Xinbao and her antics are sofa king adorable, she's moe!! The cutest baby protagonist in novels I've ever read!! Plus, she's a baby/small child (3.5-7 years old) throughout the 928 chapters of the webnovel, most of it in the younger years, which is awesome! Loved it!

Cuteness: 9.9

Story: 8.5

Just a note about the CN MTL (Machine Translation), it's definitely readable, and I was able to understand 99+% of it. However, it does take some mental agility. The pronouns are all over the place (wrong gender, or just the wrong person, e.g., he instead of she, mine instead of his, etc.), and the sentences should sometimes be the exact opposite in meaning (dunno why MTL gets it wrong so often).

https://www.asianovel.net/story/3070/

Read The Lucky Child Has Fertile Land, The Pampered Little Dumpling, The Peasant Lucky Girl Is Actually a True Daughter Novel Free (MTL COMPLETE)

https://readnovelmtl.com/novel/the-lucky-child-has-fertile-land-the-pampered-little-dumpling-the-peasant-lucky-girl-is-actually-a-true-daughter-r2tnv

Cuteness: 7

Story: 7

Some decent amount of cuteness. MC stays a small child for a long while. MTL was very readable. Only problems were the incorrect pronoun genders.

Summary

Niu Niu was secretly swapped by bad guys when she was born, and was thrown into the wild and picked up by the Zhang family couple who couldn't have children.

When she was five years old, the Zhang family had a precious grandson and thought she was unlucky, so they let her have a high fever.

The elder sister-in-law who returned to her mother's home was anxious: Who said our Niu Niu was unlucky? She is obviously a little lucky girl. If you don't raise her, I will! .

Niu Niu no longer had endless housework to do, and she could eat until her belly was round. The whole family held her in the palm of their hands and spoiled her.

The Zhang family's mother-in-law and daughter-in-law waited every day to see the elder sister-in-law's joke, hoping that Niu Niu would kill the whole family of her adoptive mother.

But she kept looking forward to it.

The adoptive mother's family built a house and bought land, and their lives became more prosperous day by day. The adoptive father also took the imperial examinations, passed the examinations of Xiucai, Zhongjuren, and the examination of Zhuangyuan, and moved to the capital with his whole family to become a high-ranking official!

The year Niu Niu got married, the powerful people in the capital discovered that the adopted daughter of the emperor's teacher was exactly the same as the wife of the Duke of Xian when she was young!

(A fierce mother, a black-bellied father, a protective and biased grandmother, brothers and sisters who are obsessed with their sister, the heroines' favorite Fuwa, a sweet and refreshing story, don't miss it if you pass by~)

Cuteness: 7.5

Story: 7.5

A little cute. Unfortunately, despite the female MC spending most of the story as a little kid, there aren't that many cute moments.

Also on Wattpad,

witchy8181 - Wattpad

https://www.wattpad.com/user/witchy8181

Cuteness: 6

Story: 7

Cuteness: 7.5

Story: 7.5

Everyone Wants to Pamper the Lucky Daughter (Complete)(Webnovel)

https://www.webnovel.com/book/everyone-wants-to-pamper-the-lucky-daughter_27254640205927205

Cuteness: 7.5

Story: 8