Visiting Disney this year for 5 nights right before Xmas. Have never visited Universal w/o staying onsite. Thinking about going on Saturday or Sunday before Xmas to perhaps see Mannheim Steamroller and visit new attractions. May even try to go to both parks. How crowded will it be? Either day better than the other? Express Passes worth it whichever day we choose? Could go earlier in the week when not as crowded but then would miss Mannheim Steamroller. Is the concert worth it and any chance there is special seating for Express Pass? Thanks for any advice.