Do standard emergency rooms use higher xray doses on infants vs a neonatal unit in delivery ?

It isn't that way: There probably is no country in the world where all emergency rooms have identical x-ray machines or where all neonatal units have identical x-ray machines, so a person who worries a lot about imaging machines has to do detective work annually and talk with each hospital's radiology services to see which ones use lower-dose (usually newer) machines and Pediatric protocols for kids' x-rays.