IF your son gets a sizeable block of time off for Christmas, he will be free to go home if he wishes.
In the regular force there is a plan called LTA (leave travel allowance). This plan allows for members that are posted away from their primary NOK (next of kin) to receive financial assistance in order to help alleviate the cost of going home to see Mom and Dad (or Wife, etc). The way it would work (if your son qualifies for it with such low time in the forces) is that they would calculate the geographical distance between St-Jean, PQ and his NOK‘s location (ie. where you live). They will then take this distance (for me, St-Jean to Toronto = 600 km) and times it by two (for the return trip). The first 200km is deducted off of the total amount (again for me 600 + 600 - 200 = 1000km). This amount is now the applicable mileage that can be used for LTA. The military will apply low rate mileage to that amount (somewhere in the region of $0.33/km) and give your son that amount. So in my example, I would have been able to receive $330 in a once per year LTA claim.
Hope that helps you out a bit Mom.
Note: Reverse LTA can apply too, your son can use that claim to help bring out to him his NOK (ie you for his grad ceremonies).
Make sure he asks his course staff whether or not LTA claims apply to him or not. He may have to wait a couple of months before being applicable for such a claim.