Biometrics can be finicky, especially for some people. I would make sure it works to your satisfaction and test it thoroughly knowing that it could be returned if it didn't work as expected for you.
I understand that your wife thinks it would be simpler than a mechanical combination, but I'm not sold on their reliability myself. I would rather pracice a little to where it is habit, just like if I ever need to use my gun. The reality is, many women are just not that interested in practicing as most odf us guys are.