Viruses mutate to spread better, not to be more dangerous, although individual mutations are random.
If children become the reservoir for infection, as it seems they will, the virus will mutate to spread effectively in children. It will probably, though, just end up as another winter virus, ripping through schools until herd immunity naturally achieved.
If it were more dangerous to children and younger adults, though, I suspect we would eliminate it pretty quickly, as suddenly everyone got on board with infection control and vaccinating the whole population.
The only way ahead, really, is vaccinating everyone, pretty much gloobally.