want to send validation code to email

I want my wife to be able to use Find My iPhone to help me find my phone if I lose it. I can have her go to iCloud on her computer and sign in with my AppleID, but to complete the login she needs to enter the verification code that iCloud sends. Unfortunately, it keeps sending the verification code to the phone (Trusted Phone Number); obviously if the phone is lost that isn't going to work. (My wife does not have a phone that will receive a text message as an alternative Trusted Phone Number for the verification code to be sent to.)

I have a Notification Email entry in the Security section of Manage Apple ID, which is where I want the verification code sent. iCloud/AppleID however always sends the verification code to the phone and nothing to the email address. It will not let me delete the phone number. How can I get it to send the verification code to the email address so my wife could access it there and complete the login?

Thanks,

Cory