Totally hot.. especially with your wife being totally hot.
When I'm with a couple, I will typically suck the other guy's cum out of his gf/wife's pussy.. why? Because it's kinky and perverse and it turns me on.
The most important thing here is this: If it turns you on (and your wife, and your playmate, etc.), do it. Fuck what anyone else thinks. That is YOUR play time, not their's. If they don't like it, don't invite them over.
So furthering the idea a little bit.. would love to see some pix of your beautiful wife straddling your face, spreading apart her labia and seeing your load sliding out of her onto your tongue.
Good christ.. that's got me so ramped up, I may have to go take care of this swelling.. :-D
Bonne chance.