Maureen, both Tammy and Heidi have given you very good advice. Even if your daughter-in-law is interested in researching her own illness, I would think that it would be a comfort to her to know that her husband takes it to heart too and knows about all the changes her body will be undergoing. Maybe you could also suggest to your son to keep good treatment records on her behalf when she is fatigued from her treatments.
On another matter, when a good friend of ours was diagnosed with breast cancer early last year, I knitted her a blanket that I had delivered to her on the day she went home. Honestly, it was just a simple pattern and nothing fancy. She loved it and her husband calls it her healing blanket. Given they live so far away, something like it may help show them you care. I wish the young couple all the very best.