the guidelines for a child's Brit Milah are the same as the one of adult apart from a few differences:

if the child is undergoing general anesthesia or sedation the child should not eat 6-8 hours before the Brit, and should not drink 4-6 hours before the Brit (juice and milk are considered food).
the child undergoing general anesthesia and sedation will need more personal guidence before and after the Brit Milah.

for more details view the adult guide
click here to view the adult guide