The headmaster has already offered to do just that.He is very supportive and wants to come to the appeal with us.
I am sorry to hear that your son missed the pass mark by so few points. I don't know the Trafford area at all (if that is where you are) but the same rules really apply Country-wide for Appeals.
Please read Etienne's Appeals Q&A. The most important message is that you must stick to academic evidence. The only other evidence that will count is for outstanding extra-curricular activity, preferably with an academic bias, such as Chess, science competitions, etc.
The Head may not necessarily be familiar with your son's record personally. It would be great to think that he will do his research, and surely he will try, but you cannot count on it. Between now and the appeal try to see the form teacher to get an update yourself. Predicted SATs, attitude to work, particular academic strengths - any highlights that s/he can offer.
You will be nervous - all of us who have been to an Appeal were shaking in our boots! However, the Head will be there at your side, and that says a great deal for your son's case.
Take those stunning reports with you and tell the panel that you have them. If there is any other written evidence of his ability and potential, take that with you.
Have you been given any advice on what information to take with you, and how many copies to prepare?
As Tom's Mum says, a written script of what you want to say, with a copy for the Clerk to the Appeals panel is perfectly acceptable. I did the same thing, and I am sure that the panel did not think any less of me for it. They quite understand how nerve-wracking the process is.
If you are in control of all that it will prevent any dramas on the day that might wrong-foot you.
Please post back for any help we can provide.