Dear HopeSeeker,
As-salamu alaykum
Welcome to the forum!
When dealing with questions such as these, I humbly feel that it is important to remember one of the basic concepts in the Quran, which is proportional responsibility and accountability, arguably underscored by a dependency on one's individual intellect, experience, wider resources and manifestation of truth.
God also remains perfectly just and I am convinced that He will deal with all of mankind 'justly', without an iota of injustice, let alone a child of a few weeks, month or years.
I also believe that children can be presented as trials for their parents and others.
I hope that helps, God willing
Joseph