Universal has (at least last year) some of the Macy's Thanksgiving Parade floats around. It's pretty neat. They have a lot of the popular ones, Snoopy, Garfield, etc.
IOA has the Grinch over there. Well worth the trip over if you have time. He's over by the Suess world, cracking jokes. I wish his little dog was there, tho!
The parks are empty. We went the weekend of 12/16 last year, and I would be surprised if there were 50 guests in each park. We got to US around 9:30 a.m. or so, rode all of our favorite rides, had lunch & beers at Finnegans, shopped at HRC, headed over to IOA, rode a few rides there, did more X-mas shopping at IOA and checked into our hotel by four p.m. We'd never seen the parks so empty -- except maybe the week of 9/11/01.
Crazy contrast to MK the same weekend, which was jam-packed.
Oops...ETA: I don't know about the on site hotels. We stayed off site.