I would stay at the El Tovar Hotel, Kachina Lodge or the Blue Angel Lodge, right on the edge of the South Rim. Its the best place to view the Canyon, and to start the mule ride to the bottom. Its also close to the Grand Canyon Airport.
If these are too expensive for your clients there are also the Maswik Lodge and Thunderbird Lodge, which is a short walk from the rim. The latter is more modern, whereas the others are fairly old.
If they have a car, they will get cheaper motel accommodation near the entrance to the National Park and the Airport. Its not practical to stay there unless you have a car though.
I have stayed at the El Tovar and it was amazing. Right on the Rim and easy access to everything in the park. The El Tovar is a veryt old hotel. During the Summer months the buses operate around the park as well as to and from Tusayan. If clients are staying in the summer months, the Best Western and the Holiday Inn are both good options. They are both inexensive and have breakfast included. I just stayed at the Holiday Inn last month. The wi-fi there was poor, but the rooms were excellent.
There is a really nice pizza and pasta restaurant in Tusayan and a Beef BBQ as well. There are more choices for places to eat out of the park. Clients would really need a car as I think any other way to get out to the Canyon would be just crazy.
There is plenty of opportunity to see deer and elk as they are everywhere. As are squirrels. We saw a Coyote once as well. Winter is a fab time to visit the park as it is not as busy. Days are cool and nights frosty, but it makes for stunning sun rise and sunsets as you can be at most view points alone. I found summer to be very busy, and hard to get parking.