It takes would take some strong avoidance of reality and logic to clamp down on people's individual safety (by mandating smaller vehicles) to 'help save' the ~ < 50 children that get run over (BY ALL VEHICLES, incidentally) every year.
So I wouldn't expect a rise in pedestrian deaths (particularly over a very short 2 year period which could just be an aberration in the data) to necessarily mean there was a similar rise in child deaths if they happen in fundamentally different circumstances for different reasons.
[0] https://crashstats.nhtsa.dot.gov/Api/Public/ViewPublication/...