I want to take photos of my sick child when he's going through particularly traumatic times
Why do you want to do that?
I feel like taking pictures of this situation will really help him in the future
It is hard to have a sick child so anything that can make the situation better is okay. If taking pictures helps both of you out, you should take many pictures.
I felt much better. Thanks 4 your concern.
I'm glad you've found something that helps you and your child get through these difficult times. You should see if these pictures can help other people going through something similar so you can share this feeling with others.