I have had your family in my thoughts for some time now, and I'm sorry that you are having to wait for this scan. Having been at the mercy of the NHS many times with regards to the children, I can empathise.
I hope that this helps, but I am friends with a lady who has no use of her right arm and she gets along very well. In fact, it's not until you meet her a couple of times that you're aware of it as she has adapted so well having been like this for most of her life.
I know that no-one wants their children to suffer in any way, and would not hesitate to change places with them in an instant, so the best that you can do for your family now is to bite the bullet and accept the offers coming from your friends here on the forum. I know that during these times when you're waiting all you do is go over and over all the possibilities and this must be having a bad effect on your family life. Anything that you can do to reduce this would be for the best.
Good luck to you all and don't forget that we're here for you.