Can I evoke my ability to make decisions immediately or go to court?

It depends on the state you live in. Make multiple copies, keep one in your purse, keep one in your car, keep one at home.... You need to contact a local Senior Center to find out. In Alaska I don't need to file with the court, but I must have a copy in a moments reach at ALL Times.

In Alaska, all I had to do was have a Notary, notarize, and my Mom sign in front of the Notary. But check with local Senior Centers, your state may different.

I don't think you need anything other than having copies with you at all times. Every time you make a financial or medical decision, payment, deposit, just be sure to sign as "John Doe, DPOA on behalf of Margaret Doe" and you should be good. Keep good financial records and receipts especially if there is an estate question at some point in time.