Incall is still pretty limtied in Vegas, so many hotel rooms.   However, there are ladies who do offer incall, such as Kit, Jade, Jackie Jewel and Logan.  They share a place which is close to the strip with another lady that I don't know.   Nikki Avalon offers incall I think, there are others as well that I don't know as well as the above mentioned ladies such as Ariannia, Nicole, and Roxanne.   An option might be to get a second room, then the whole of Vegas is open for you.  Depending on what you like or want for your nephew any of the above would be a great choice.

I would definately consider Roxanne, and Nikki Avalon.  Roxanne has her own place which is very nicely decorated by the strip.  Her website photos were taken there.  Nikki uses a hotel from time to time.