The question I have that you didn't elude to is, what does your wife think of this? She's the most important person in this equation, and her feelings should be considered above all. If she has trepidations, back away, it won't be worth it.
On the other hand, if she's interested, how do you feel about it? This type of relationship takes a tremendous amount of trust on the part of the husband.
If both of you are up for it, I'd start with baby-steps. First night, dinner and sex, then she's home by a decent time. Next time, stretch it a little. At any time, if it's not going well for either of you, call an end to it.
It could be a lot of fun, but it could also be a real challenge to the core of your marriage.
Best of luck.