I picked castle for my son because I guessed that was what he would prefer, I was wrong. Better bet to ask first maybe, but regardless he had a fantastic time.
Make all of your reservations as soon as you check in. Things fill up! Also, I totally recommend the birthday package. I think it's an extra hundred bucks, but they get this whole bag of cute stuff including a bear, blanket, pillowcase, a banner for the door, and a toy. Plus a gift card for any of the gift shops. Personally the original hotel better. We've stayed in both. But really it just depends on which theme you want! More choices at the original hotel.
All reservations are made with open table. The front desk will give you a QR code to scan they make it very easy. You can actually go back and forth between the hotels. We liked the castle because they have a fun pool and the LEGO movies play on the big screen with a nice viewing area. But that's just our family.
The castle hotel is the newer of the two. Reservations for the restraint happen in open table. Which hotel is better is a personal preference. I would probably pick to stay in the Lego hotel if I go back again.
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