I have always been a proponent of a very small amount of oil (glove oil and/or shaving cream) - too much and the glove will gain weight/pick up grit. I would just spend time working (flexing the glove back and forth) the stiff parts (the heel joint, thumb hinge area and inner pocket) while sitting watching a game, along with a bit of light oil on the tough areas, then just get out and throw with it. You can also of course wrap it with a ball (sometimes a softball works best if it is a larger glove, FYI) in the pocket with rope or straps for a while if the pocket isn't great/it is not laying down right.
If you have a sunny porch, put it out for a couple hours to absorb some sunlight then bring it in and work it while it is warm. Your son can also speed the process by wearing it inside (while watching TV or whatever) and popping a ball in the pocket - he has to "break in" the inside finger part of the glove as much as you can break in the outside. Of course at the end of the day, nothing beats throwing & catching ultimately for breaking in a glove the rest of the way, but at least where I am, alot of days recently have made it tough temperature wise to consider going out for a catch....
Now catchers mitts are a different story altogether - I dunk those in a bucket of water to start with, but that is a much more tortured process not really relevant to your needs....