They could go for a hike or a walk. Hikes in a nearby forest are a great way to see nature on a daily basis and free of cost. If in an non rural area, such as a city, walking around town is a great way to get more physical activity! Another great way is to visit a zoo; most zoo have walking distance between the different animals. You can get both the active and nature in that as well.
(And I can't think of another one sorry)
Attend doctors appointments with the mother to help listen to treatment options, ask questions, and discuss any alternatives they can consider.
The answer medical supply hope this helps stay safe :)