When are you going? If you sign your youngest up for the free Lego Club magazine there is a coupon in there for kids to get in free.
Also if you can stay at the hotel, do so. It was the best part of our trip there. I have a 13 year old and a 10 year old. Best part for 13 year old (who loves legos) was miniland. The rest of the park was really for smaller kids. My daughter enjoyed the park more then my son but even for a 10 year old it's pushing it. The hotel has a lot to offer for older kids too that love legos.
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