A really tricky issue. They’ve spent most of their lives managing their own money and now its being asserted they can’t. Moreover, there are technological risks now that never were. And then the scammers (IE; people portraying themselves as soldiers in Afghanistan needing money). Finally, the reticence of an older person to admit, even when they know they’ve problems, that they need help. IOW, shame.
Here are some ideas/suggestions:
1) Use debit vs credit cards. This will limit liability to that which is in the account. And don’t keep a lot.
2) Prepaid cards. Again, they’re limited to what’s on them. Some allow for loading/reloading via direct deposit, transfers or checks deposited at ATM’s.
3) Check out True Link. A card special for seniors. The “administrator” (ie; family) can set per-purchase or per-day spending limits, can block charges to specific merchants/charities. You could block purchases over the telephone.