They have made changes to the policy so don't get caught out! You now have to register online at least 24 hrs before you visit - when you do the online form it then says you will need to take GP / Consultant letter to confirm!
The online ride access policy doesn't say evidence must be from GP / Consultant so I querried this and they have confirmed to me that the evidence I have ie letter from the school nurse (special school) detailing ds diagnosis and need for a pass will be ok along with his statement.
www.legoland.co.uk/Book/Terms--Conditions-new/Rides-Access-Pass-Terms-and-Conditions/