The free museum on the ground floor is a good start. The 3rd floor museum is good, Get a players card from player services and the museum is free. There are even some cars for sale. Inexpensive activity if you don't want to gamble.
You have to keep going up and up in the hotel to eventually get to the Car Collection. We did not have a players card and therefore, did not go directly into the collection proper, but we could certainly see quite a bit of the collection from other areas including the gift shop which was worth a browse.
Stopped by with friends to view the car collection. Lots of cars that I've seen before and some I didn't know were ever made. I loved the Classic Cord...Red....WOW! So many others. Cost is $2.00 for the 3rd floor museum. The first floor area is FREE. Not sure how that works, but it's was worth the price. Nice gift shop...