I don't really know what's in store during couples sessions--I'm guessing it depends on the girl as well. If they are open to couples, they'll list it on their website. I've seen a few Vegas providers' pages that have a couples rate. You'll probably have to do some searching though. Unfortunately for clients, there really isn't a way to find out what a provider looks like in person unless you pay their full rates for a meet up.

I understand the aspect of seeing the woman makes casino girls appealing, but I'd advise against that for a number of reasons. For one thing, that's one of the main ways Vegas police will conduct stings. Also, you may have trouble finding someone game to have your wife in the session as well. Finally, a casino girl is a way to put yourself at risk to being robbed or hurt. On a side note, Casino girls are intentionally hard to spot. Hotels/casinos do not condone women offering "services" on their property and they'll remove someone they believe is doing so. So casino girls will usually come to you and go about things rather discreetly. Further, I don't think anyone will approach you if your wife is there as well.

I guess my overall advice would be to look for women with higher rates. In my experience, these women seem to have the least amount of surprises in the looks department. If you're willing to open up the wallet a bit, I second what the other poster said about TLC and finding out if any pornstars are in Vegas during your visit. Finally, to address your questions about services offered, the best way to find out is through their website--if they offer anal, it will be mentioned on their site by the mention of "greek" in their rates listing. I'm not sure what the best way to ask a provider is--I've never asked any questions prior to meeting. I will mention that you should wait until you've been screened before asking questions. If you ask things like that before, you'll likely be ignored.