Firstly, be sure your wife is cool with the idea of dancing. Really and truly.
If she really is ok with it I would recommend you and your wife look for a club that is not all nude, look for topless clubs or even bikini. Nude clubs tend to be much more seedy in general. Some clubs are more stage-centric- meaning if your wife can move well she may be able to dance onstage for money, and forgo lap dances altogether. She may make less money by not doing lap dances, but it is all about doing what you are ok with. Visit different clubs at prime hours (evenings) and check out how much $ you are seeing being thrown down onstage. More is better, obviously.
There will likely not be encouragement from management at this club for her to do any more than just a lap dance. Pressure will mostly be from customers, however, quite often, in nude clubs, management is willing to look the other way when it comes to stuff like this. The more conservative the club the less she will experience this sort of thing. Dancing in cities that boast McDonalds as the best fine dining in the area will be dirtier and will bring in less money.
Surprisingly, girls in full nude clubs often don't make more money. Dancing can be a quick and easy way to make cash, though the money isn't what it used to be in any clubs anymore, so it's best to stick to bikini or topless bars. Often the best money comes from older gentlemen who want a muse who is still a lady- keeping some mystery can be a very good thing. Look for clubs with older clientele, in or nearby wealthy neighborhoods. If your wife starts dancing tell her to look for the gentleman sitting by himself- check his shoes and watch to see what kind of money he has to spend.
Finally, if your wife really doesn't wear a two piece bikini at the beach I would think long and hard about asking her to do this. If she is not comfortable with showing her body (even if it's perfect!) she won't be comfortable/confident onstage and she'll end up making less money and just resenting the whole experience. This could be really bad for your marriage.
Nude clubs are poopy and gross. I dj'd at one for a couple weeks and went right back to djing at bikini bars where the environment is not creepy. Hope this info helps. Oh, and if she's going to be doing lap dances have her go look at the area the dances are done in. If they are too isolated from the eye of security- that's no good. Good luck.