Obviously, you've been to Las Vegas before. Still, I'd take a moment to decide if you really need to spend 7 days in Las Vegas. That's a long time to be there. As many people have noted, prices for hotels and everything else continue to rise. If you not gambling and winning, it's an expensive town.

Personally, I'd split things up by spending maybe 4/5 days in Las Vegas and 2/3 days in Flagstaff/Grand Canyon. Doing that might help stretch your budget, as you might be able to find cheaper hotel rates in Las Vegas during the week.