In view of Dr. Khan experience for last many years, he recommends the optimal age of circumcision in children is under 6 months of age. He advises to the parents to book their children for the circumcision as soon as posibble so that they will not miss this optimal age of an infant. 

Medical literature  supports this concept.

"Infancy presents the best age for circumcision. It is associated with substantially lower costs, lower risk of complications when performed by an experienced operator in a clinical or other appropriate setting, and lower lifetime risk of a variety of adverse conditions and infections"

Dr. Morris wrote in his recent review. 

BMC Pediatrics 2012 DOI: 10.1186/1471-2431-12-20