Thank you so very much Mike and MsL for your suggestions ... I really appreciate them and will definitely follow the advice you have given me!!
From what I believe, after speaking to my mum, she has booked the seats that have the extra leg room that are at the front of the plane. I think they have about twice as much leg room as a normal seat so hopefully that should help as I can't bend my knee too much due to the pain and Dystonia.
We are taking my wheelchair with me as there is no way I could walk all the way round Vegas (I struggle enough short distances!!) so I shall talk to my mum and see if she can arrange for me to go onto the plane in the wheelchair to try and minimise any walking I have to do. When we flew to see my grandad in the beginning of my RSD journey, I was in a wheelchair and they were really good and got a ramp and hoist to get me onto the plane.
I'll also make sure I drink plenty of water to try and get rid of some of the swelling. I see my Physical Therapist's next week so will speak to them and see if they can suggest anything else that might help. My mum was also going to speak to my Pain Management Doctor to see what sort of medications I should take before and after the flight to try and prevent any flares.
Thanks again for all of your help - I really appreciate it and will definitely let you know how I get on flying with RSD and take some pictures for you all!