Thanks Ben10 - will have a look at that.
The problem we have is that DTS2 is very astute and is picking up on things which are said about his brother. We are having to explain to others that DTS1 has SN to explain behaviours etc and DTS2 is overhearing and asking questions. DTS2 will understand - whether DTS1 will I don't know but we can at least tell him that that is the reason he doesn't like loud noises (for example). I've got a meeting with his school next week so I'm going to see if they have any suggestions too.
We are going on holiday to Disneyland paris in June and I think we are going to try and get the pass to queue jump to avoid problems. However I know this is going to provoke questions about why so that is partly why we are thinking about telling the boys now.