I have found two things are effective in circumstances in which there is this much pain: prayer and acts of service.

Does your church have a prayer chain or prayer e-mail chain. I would encourage you to put John's father on this.

One thing that helped my family through this was the churches out pouring of support. We had people sign up to make meals three times a week, and we had people who offered to clean the house, perform child care (take John out and distract him for a bit), and be on hand for car-pool as necessary etc.

If the father is considering chemo, the treatments way require sitting in one place for hours at a time it helps to have people provide entertainment or offer their services for driving (books, games, shows, audio books, or even just their presence.)

The Christian community is vast, it is worth taping into and if your church cannot, perhaps contact additional churches for support. I have always been astounded by the generosity of Christians when called.

Hope this helps. So sorry for the hurt this family is going through.