I want to watch...

All of the above would be fun but I would definitely do her doggy style pulling her hair so she's looking right at you; make you watch her face as she gasps and orgasms and cums hard and multiple times on my cock.
 
I have to admit that I've often thought about what it would be like to do a guys wife in front of him.

In my mind, your wife and I are both naked on the bed and I tell her to get on her hands and knees in front of me. I position myself between her legs, place my cock at her wet opening, and then look over to you. I see you staring, wide-eyed, at her pussy with my cock ready to push into her. The look on your face says it all: "do it!" I grab your wife around her waist and push myself inside. Ah....I love the hour-glass view of your wife's torso, shoulders down to her ass, as I slide in and out of her. I love leaning forward, reaching around an squeezing her tits, and playing with her nipples. And reaching under and playing with her clit with me deep inside of her pussy. I pound and play as I feel her excitement growing and growing. I pound harder as she begins to moan. and then... I love feeling her cum on me: the clenching feeling of her pussy around my hard cock. The excitement is too much for me and I return the favor by unloading inside of her pussy. We stay that way, letting our climaxes subside.