Best wishes to you and your son. Cancer, as you already know, seems to abhor oxygen. Thus EWOT (Exercise with Oxygen Therapy) is effective (as effective as food-grade H202 (peroxide) and easier to tolerate.
I don't know your financial situation. If you can afford $1,000 you might do what I did. You might buy an oxygen generator (see www.betterthanair.com/product.html) and purchase a personal oxygen generator. Your son can stationary-walk, do a small exercycle, walk on a treadmill, etc. for 15 minutes a day and his little body will be very oxygenated - and maintain a ph better than 7.2.
If this is too expensive, see a doctor who will prescribe an oxygen bottle you can rent for about $30 to $50 a month that your son can use during exercise. The testamonials are profound. I hope this helps.
Bart