Activate FaceTime and Messages on Wi-Fi iPad with email address only?

Is it possible to activate FaceTime and Messages on Wi-Fi iPad using Apple ID’s email address only?

Someone has Wi-Fi Pad but doesn’t have an iPhone. Although there is a phone number associated with the user’s Apple ID, that phone number is not associated with FaceTime or Messages because it is not on an iPhone. When trying to activate FaceTime or Messages on the Wi-Fi iPad, the Apple ID email address is shown, but the Sign On option is greyed out and neither Facetime nor Messages can be activated with that email address only.