One of my main questions entering this pandemic has been: Are the vast majority of children not getting CV at all, because they have some kind of immunity (for whatever reason), or are they getting it but the vast majority of that population having low to no symptoms.

I've seen anecdotes about kids and CV, but I was wondering if there has been any studies that may gain insight on this?

As far as places that have done widespread testing throughout a whole population, I am not aware of one that has done a lot of minors. The Diamond Princess did test the few minors they had and found that out of 41 children, 6 tested positive with 4 being asymptomatic.
https://cmmid.github.io/topics/covid19/diamond_cruise_cfr_estimates.html

I have not seen a lot of information on these questions for serology tests either.

The reason it seems like a critical question is how it relates to school and youth activities. If kids are not getting sick at all due to some broad immunity, going to school and/or doing youth activities would have a low risk of exposure to everybody else who could be vunerable. If kids are getting sick but almost universally not showing symptoms, that makes them a potentially dangerous vector for spreading the virus.