The only requirements under the Guardianship and Administration Act of WA are:
- You must be at least 18 years of age; and
- You must have full legal capacity.
According to the WA guide on powers of attorney, 'full legal capacity' means "the capacity to make a formal agreement and to understand the implications of statements contained in that agreement."
If you can do that, then apparently yes you can.
I would suggest disclosing your status to the donor (or reminding them) to make sure they are happy to proceed.