Oh, one piece of advice for going to Las Vegas in the summer months, stay indoors!
My wife and I visited in June and the temperatures got up to 120 degrees!
That's something we stayed out of as much as possible and when we did walk across the street, our shoes would stick to the pavement on the crosswalk...
Very Hot in Las Vegas during the summer.
If they do plan on walking around a lot, make sure you tell them to try to walk through the casinos to stay cool.
They will need to get a humidifier for their room, have them check the front desk during check-in to get one sent up. It makes a big difference for keeping the room comfortable.
Any extras they plan on having in their room, they should ask for during check-in at their hotel.