One key thing to remember about powers of attorney: they are only in effect while you're living and are useful if your mental capacity is diminished or you're sick or just not able to otherwise care for yourself. However, the common denominator in all of those examples is that you must be alive. Immediately upon your death, the bank will block or "freeze" your accounts and only allow payment of things like utility bills, funeral expenses and so forth or as authorized by your Estate's executor.
It obviously depends on the rules at different banks so talk with your personal account manager at your financial institution as some banks treat accounts you hold jointly different from those in your name only. They may not block or "freeze" accounts in which you're a joint owner. So, you could potentially have all of your accounts held that way. Another option, and obviously you'd want to talk to your lawyer/tax advisor/financial planner, is perhaps setting up a trust.
Beyond that, for monies held outside of a registered account like an RRSP or a TFSA which let you specifically designate a beneficiary that is outside of a will, those are the only real options other than having a will (you really should have one, even if it's one you used will creation software to make and had notarized or a holographic will you handwrote).
Cheers,
Doug