AItaly: Where to spend time in Italy
I'd definitely hit Rome but also remember Venice, maybe a day or 2 there also. If you have the opportunity hit theItalian Alps, beautiful country at the North end as well.
ALas Vegas: Las Vegas or Death Valley for stopover on way to Yosemite?
If it's just for one night then stay in Las Vegas. There is too much to see at Death Valley. Or maybe a night in DV would entice you two to come back and visit it at a later date. Personally I'd do the over night in Vegas. ...
ALas Vegas: Is it better to stay on or off the Las Vegas strip?
First trip? On the strip. Favorite...Wynn Hotel Las Vegas..very nice property but a bit expensive. If you're on a budget then get a room at New York New York Hotel & Casino or Circus Circus Hotel & Casino....