Q: why am I not receiving ask to buy notifications?

I use a MacBook Pro running the latest version of Mac OS X Yosemite. I have an iPhone 6 (iOS 8.1.1) and my son has an iPhone 5s (8.1.1). My wife also has an iPhone 6. I've set up family sharing, designated myself as Administrator and entered the appropriate credit card info. I then set up an iCloud account for my son (13 yrs old) and sent an invitation to him to join Family Sharing. I've also set up my wife as Parent/Guardian so she can approve purchases as well. When my son wants to make a purchase from his phone, he taps on Ask to get permission. My wife receives a notification, but I do not. Anyone know why this is and how to fix it?