My DD and I were there at the beginning of December, and we rode most everything single rider if it had a wait. Since many of the rides are virtual reality, it didn't make a difference that we weren't sitting right next to each other. I don't do the big coasters, so she did single rider on those by herself (Rock It Roller Coaster, Hulk, etc). I hope they have a great time! Tell them they have to share one of the giant donuts in Simpsons land.
Also, they can always decide to purchase EP when they see how the crowds look when they arrive.