Great link above.
Personal preference, The Premium Package with the upgrade to Bullion Shoulder Boards. Just remember to ask your son what cover they are all wearing, the package comes with the Beret so you would have to add on the Service Cap (Bus Drivers Hat) which is another added cost. Also make sure he either has shoes or if he will need a new pair. Good your ordering now in case anything needs to be sent back because of size or damage, plus there is always a rush to get tailoring done when it gets close to graduation.