Disneyland Paris - GP letter refusal

Hi

I have a 14 year old son who is on the autistic spectrum he was diagnosed at the age of 5. my son is high functioning but since attending comprehensive school he finds things hard to cope with and will have meltdowns when things get too much.

We are due to go to Disneyland Paris in a few days and 2 weeks ago I went to my gps to ask for a letter explaining why my son will find it difficult to queue. The letter my gp wrote didn't explain much and I was charged £20 for it. Last week I went back to the GP and said I was unhappy with the letter to the receptionist who told me to speak to the practice manager. Well to cut a long story short she wasn't a lot of help and in the end I had another appointment to ask for the letter to be rewritten with the things in it as I requested the first time. 

When I went for my appointment she told me that it was only my say that my son had these difficulties. I told her I wasn't going to waste her time taking him for things that were part of his lifelong condition. All she did for me was put in her letter that she attached a copy of a letter from our social worker  (which our social worker had kindly sent me) and said that this letter outlines his difficulties. I was so cross that she made out that I was a liar and I was just saying these things.

my question is will this be enough proof for disney for less queuing time? I have the rubbish GP letter with the social worker letter, diagnosis letter and I could take an OT report as my son was assessed through he summer to see if anything could be done to try and lessen his anxieties. 

I'm thinking of changing gps and writing a letter of complaint. 

Many thanks

sarah x