We did the same thing before our first trip. Makes the lead up to the trip even more fun! Watched the same ones you listed, plus Twister.
We were glad we had "done our homework" but the first 3 characters encountered: Lucille Ball, Marilyn Monroe, Betty Boop. Kids had no idea who any of them were. They did enjoy the Lucy museum though (9 and 11 yrs at the time). So with that in mind would DVR a couple of I Love Lucy shows and google Marilyn and Betty before leaving so they know who they are. Not sure if this character is still around, but our 4th Character was Doc and he posed with the Delorean. DH and I got a pic with him, kids had no idea who he was either and would not get in the pic.