I was there 6 months ago. While I didn't go to any car museums, I can tell you that Club Paradise has some of the most incredible headlights you've ever seen.
Grab a phone book and open to about the middle,and make a few calls....
There is always Hover Dam if you have not been there,pretty cool...take the tour there
I used to live there for 10yrs...non gaming related....
Can do a one day trip to the Grand Canyon on a bus tour, or the flights over it can be good too. Hoover Dam is a good way to spend an afternoon. Night clubs...heard the Hard Rock has a good one as well as the Palms, left before i was old enough to do all that. If you are into roller coasters, the one on top of the Stratosphere, Speed at the Sahara and the one at NYNY are good. And have heard Cheetahs and Olympic Garden were good strip clubs, but don't have much experience on that one. Hope that helps.
The 2 hotels are only about 1/4 mile apart on opposite sides of the strip. The car show is like $5/ea, but if you're feeling cheap, here's what to do. At the entry way right at the strip is a greeter desk inside the doors. Tell them you want free tickets to the car show. They will briefly pressure you to buy time shares or something. Just say, "No thanks, give me the tickets" and go enjoy. You will have to walk to the complete back of the casino, through the elevators up to the hotel, through a few stores, up a short escalator, and then up a few floors in an elevator.
Do as Jack said and get the free tickets at the Imperial Palace. There is also a coupon for it in the visitor guides that is free.
I would suggest going to see Hoover Dam, but not the tour. It's pricey and not worth it anymore since 9-11.
If you like Fords and Shelbys there is his muesum in town out by the dragstrip I think, and there is a gun range that lets you shoot a bunch of different weapons for a relativiely small fee considering the cost of ammo.