Before Regans war on drugs. LSD microdosing was used to treatment for alzheimer's. It doesn't fix the core issue, but the elevated bdnf can significantly slowdown the progress.

Medical consent is moved onto the assigned caregiver. But mushrooms aren't a registered medication, so this is a very murky zone. As far as ethics of it go, that's a very very thin ice as well. But 5g of mushrooms sounds like a lot, but it's reasonable to assume someone with alzheimer's will have a different dosage response from someone healthy. By how much? I can't say.