Your "mid Strip" hotel choices include:

Wynn
Palazzo
T.I. (formerly Treasure Island)
Venetian
Harrah's
Imperial Palace
Caesars Palace
Flamingo
Bally's
Bellagio
Paris
Planet Hollywood

I recommend that you check a couple of "discount hotel" websites to get an idea what the rates look like for the dates you'll be in Las Vegas.

Here's one I've had good luck with: http://www.i4vegas.com

Or you could try: http://www.hotels.com

As to a car rental... if you'll just be picking up chips along the Strip, you can probably get along without a car... if you plan to travel downtown, off-Strip, and to some of the outlying casinos, you'll definitely need a car.

I'm sure you'll receive plenty of suggestions from the readers of this ChipBoard.

Good luck with your plans and have a great time in Las Vegas!