Almost 4000 children die each year from drowning in the USA, with double that having a non-fatal drowning [0]. Note that non-fatal drownings can cause long-term health problems. They haven't banned pools yet, so it follows that, as a country, the USA considers 4000 dead children an acceptable risk of having open water, such as rivers, ponds, and pools. And bath tubs, I suppose.

Now with that number in mind, how many children are expected to die if all of them were to be infected with covid-19? I found it hard to find some numbers about this, in my country all corona-deaths of people aged 49 or less are grouped together these days because there are so few that they could be traced to individuals otherwise.

[0]: https://www.cdc.gov/drowning/facts/index.html

It's the job of those imposing restrictions to define the risk.