canadajamaica.... congrats to your boyfriend, must be a good feeling to have his son with him soon... other than the passport and COPR (conformation of PR paperwork he should have gotten with the visa), he should probably have the travel letter saying he can 1) travel unaccompanied if he is a minor and 2) has permission to leave the country to the father, from the mother (or whatever court documents might exist around custody)...
other than that it's a fairly simple process, hopefully he's not too young to be intimidated by it, the custom officers are a bit brash at times, but it's really just a technicality to answer some landing questions... he should know what his address in Canada will be, contact information (full name/phone number of his father) and other basic information that was asked on the application (simple things, like his age, his grade ect)... for an older child most of these questions will be simple, but if he's younger his family may want to prepare him for the questioning...
Also, it's an obvious one to us, but make sure they don't send any alcohol with him unless he's over 19!
hope that helps