We did this a couple years ago, and it was great. You have to decide which "Grand Canyon" you want to visit. Yes, of course, it's all the same canyon, but the tourist developments can be broken down into a couple groups:
National Park, South Rim: This is the most popular location, and people often don't realize it's not the only option. It's very touristy: Chain hotels and so forth outside the park. During the summer months you cannot drive your car inside the park -- instead, you must ride their bus; it's that crowded. The park offers five (five?) hotels and lots of restaurants -- you'll be closer to civilization in the South Rim. In addition to hiking, you can ride mules or take part in ranger programs. Do not expect to see wildlife. Unless you plan serious hiking, two full days here is just right. You also have the option of staying in Williams (Williams?) and riding the train into the canyon area.
National Park, North Rim: This is the less visited area, but it's closer to Las Vegas. It's not "built up" at all -- you'd have to drive probably 20 miles to get to a restaurant (the Grand Canyon Lodge does have one nice restaurant one deli/pizza place, and a bar). The views are wonderful, and it's about 10 degrees cooler than the South Rim. The national park rents cabins that look like they're made from Lincoln Logs, while mule-ear deer and chipmunks run around everywhere. Hiking, mules, ranger programs; also The Cookout Experience is worth an evening of your time. Two full days here is just right, and you should bring sandwich makings and lots of water/sodas. This rim is closed in winter.
Realistically, if you don't already have reservations, you're probably not going to get a room/cabin in the national park for this summer. If you can get reservations inside the park, that's where you want to be. Your accomodations will be rustic and a little expensive, but you're paying for the location. You'll be able to spend more time in the canyon and will enjoy it more if you stay right in the action. For the Grand Canyon, outside the park is really a distant second-choice.
The Western Rim is owned by the Havasupai Indian tribe. They have few hotels, etc. for tourists in the area, but they do have the very expensive glass overwalk. If you're in this area, another option is to hike down into the canyon -- all the way to the bottom -- where you can camp or stay in their hotel. There's a waterfall where you can swim. You can either hike out, or -- if your pockets are very deep -- you can helecoptor out.
We stopped at Zion National Park on the way to the Grand Canyon. It was also a wonderful place; I would've liked to stay there longer. And after the Grand Canyon we continued on to Page, AZ, where we saw Glenn Dam (2nd largest dam; 1st biggest couldn't have been much more boring) and Antelope Canyon, which was wonderful -- absolutely other-worldly. Then we went on to Cortez, AZ to see Mesa Verde National Park, which I personally enjoyed more than anything else we did in that area.
