That Diamondback 24" looks very nice, and with BRIFTERS?
Of course, kid's hands may or may not be strong enough for the brifters. But, I'm not sure the paddle shifters on the Fuji Ace were any better.
I posted a couple of links to 650c bikes in this thread. Some have finished (and you could look for new bikes). But, it might be worth looking at.
https://www.bikeforums.net/fitting-y...zing-help.html
Hmmm... The two Treks and Cannondales don't really have kid's geometry.
But, the Little Giant and the Felt F95 (which haven't sold yet) would be worth considering.