July - Vegas for 4 nights, where to for the next 5?

[Zippee]

I'm taking my wife to Vegas in July for her 40th and we then have a further 5 nights available but have no idea where to go after. Was thinking possibly flying on to San Fran, maybe hiring a car and heading to one of the national parks for a day. I really don't know the US well and would love any advice people have on not only where to go after but also what are the must dos in Vegas itself?