My 6 yr old DS will be assessed for ADHD/Aspergers, what to tell him?

[Nightingalemumoftwo]

DS2 attending a specialist centre for observation/assessment/diagnosis.
We will spend a few hours there; what do I tell him is the reason for us going there? How do I word it without making him feel that there's something "wrong" with him? I want to word it the right way.
Any advice welcome.

Does he perceive himself as being different? Is there anything he worries about or struggles with?

For my DC at that age I might say something like "We're going to see some people who might be able to advise us to help you cope with loud noises and the way you get "jittery" sometimes."

Otherwise just say its a special checkup. Lots of children have check ups for various things at about that age: speech, hearing, eye sight etc.

Thanks. His teachers say that he is aware of being a little different to his peers, and that might be confusing for him.
Occasionally he has said things like "I'm a weirdo", but is otherwise a playful, happy, cheeky boy who will often act the clown to get laughter from his friends.
I want him to come to the specialist centre feeling relaxed.