Why are you leaving your wife with power of attorney? Will it be for everything or something specific? For what potential purpose?
Legally, I believe any notarized document that has been drawn up to include what the power of attorney can be used for would be considered valid. At least, the power of attorney documents that I have used for my wife for closing on our properties has been fairly simple and simply signed by each of us in front of a notary and accompanied by copies of our driver's licenses.