Thanks everybody for your help!

We have booked flights and (most of the) hotels (many were already full or filling up quickly!)

Two more questions:

1) rental car. We just need a mid-size car for the 10 days in Nevada, Arizona and Utah. (LAS - LAS) There are so many car rental companies and the choice is overwhelming - does a "consolidator" website for car rental exist just as for air tickets? We don't have any loyalty to a car rental company - any reliable company is good for us.
2) Choice of hotels in Las vegas is also overwhelming. We just need a decent bed for the night for our first/last nights in the area - any recommendations?

Thanks again for all replies!