I like the idea of watching facial porn together to show her how enojyable and fun it can be. There are so many facial scenes when the girls/women giggle and laugh when getting a big, fat facial -so nice
I'm in no relationship at all, but the approach of watching porn together worked very well for me before

But if you have the permission of your wife to fulfill your fantasy "outside" - how about searching for bukkake events, if there are any in your area? And if you feel comfortable with the situation of being in a group of wanking males. That would'nt involve the dating thing with the woman and she'll definately know what she's into.