Both parents diagnosed with cancer

My mom was diagnosed with lymphoma in 1998. In Feburary, 2003 she began workups for a bone marrow transplant. She is in and out of the hospital every 3 or 4 weeks. In May my father was diagnosed with Lung Cancer and is currently receiving Radiation and Chemotherapy.
Dad has not worked since May 16 and spends most of his time in his recliner. I know that both chemo and radiation taxes his energy stores, but some days he feels pretty good but doesn't do anything at all. This concerns me because I don't want him to just let go and let the cancer get the best of him. At the same time I know that he needs to rest. My mom tries to stay busy when she is home and will try to accomplish little jobs around the house until she feels tired. Does anyone have any suggestions about trying to keep dads spirits up and maybe have him do little tasks or something other than sit in his chair and dwell on the cancer? I think sometimes too that I am just used to seeing him working all of the time and the fact that he has to rest often is not his normal routine. I am still learning how to cope with both parents having cancer and getting them to where they need to be. I appriciate any responses.