Can we purchase gun(s) in vegas for son

You can certainly do this, but you cannot take possession of them. The shop owner (with FFL) will have to ship them to a shop in the state you reside in that also has a FFL. Gotta do it in your name however. So do you have a dealer in NY you can deal with? If not it might be easier to just forego the favor for your son and let him get the shop in NY order from the western state. Feds are looking closely at weapon transfers these days since the Fast and Furious debacle.

This sounds sketchy. Your son will need a licence in NY to own them. If he has a licence why doesn't he just buy them there? If he is looking for a particular weapon, he can gget a gun shop to order it from the manufacturer. Since you don't have a permit if for some reason you get caught you will be facing stiff firearms charges in some states.

But if you feel you must, look here for the rules governing transport of firearms

Now I will settle back with the popcorn

"Sounds like trouble" might be the understatement of the year.