I've no personal experience but I've read that Providers will not agree to this unless they've been contacted by the SO.  Not sure if LV is different but sure avoids a bucket full of problems for the provider.
I'm sure it's been discussed on a TER board before.
skb

You are probably fortunate to already have someone lined up since the two of you have never done this before and I hope you have a blast. I think the answer to your question would be the same as when you see a provider by yourself, specifics will have to wait until after you meet. I would not stress over it too much beforehand, the provider is going to be just as curious about boundaries as you are, just be patient.

Send me a private message here, with the name of the provider.  Las Vegas can be a scary place, and I know of a few ladies that work with couples.

I've not personally partaken with my partner, but know a lot of the ladies well enough to recommend.  I can't do it here though, due to the rules of the board.

After the passing of the envelope, why don't you excuse yourself for a few minutes (go to the can, take a shower, take a long time pouring drinks, etc).  During this time your wife and the gal can discuss, and agree upon the ground rules for the meeting.  Providers who visit couples are used to them, and will most likely respect the boundaries.

I hope all three of you have a great time,

jazz32

Dear Tek
Let's see, you're a newbie, your wife is a newbie and the lady you've contacted is a newbie with couples and she has SOME good reviews.
Please contact Little Phil, his offer of help should be taken. To all newbies, when an experienced hobbyists offers assistance to you please take them up on the offer.