Hi We moved a few months ago with DS1 (4, asd). Also 5 minutes walk away, so no school change.I found it helped to completely remove him from the situation for a few days. I felt that being surrounded in boxes and stress would not help him settle. He went to MIL's a few hours away, she had both DS's for 3 days. Luckily he is used to staying at her house as we have always done so regularly. I could then get his room set up and tidy, his own bedding on, his own toys around etc. before he came home. We also moved in term time so he could get straight back into his routine on return from MILs. It took him a few nights to feel comfortable in his room, but it all went much better than I expected. Good luck,
have only ever done international or at least national moves with dd2, so was about to launch into my standard advice but what ll says sounds sensible. you won't have any issues with transfer of services etc, so i'll shut up! lots of prep though. start talking about it in plenty of time if she's capable of understanding. chuff chart until moving day so that she can see how many sleeps until she gets a new bedroom etc. visit the house, show her which bedroom will be hers. show her which bedroom will be yours. show her where the bathroom will be. introduce lots of references to the 'new house' at every opportunity. pref in a positive way! cool stuff in the garden? and maybe some reinforcement that nothing else will change - 'we will have to get x round to play and see your new house when we move' 'how fun to live on the same street as grandma!' etc.
Agree with the prep stuff if dd can understand. DS1 has almost no understanding and no speech, so I couldn't really prepare him at all. I did take him to one viewing though (once we had already agreed to buy). He was immediately at ease in the house and loved going up and down the 2 flights of stairs (he is obsessed with stairs). We used to walk past this house on our way to school, and he actually tried to run up the garden path one morning after the viewing - I took that as a sign it was the right house!
We moved last september with 2 dd's (one AS and one ASD), we involved them as much as we could, they went to the viewing, picked their rooms and we were lucky enough to have the keys early for the new house to decorate so i took dd2 almost every day whilst slowlly moving things in and decorating their bedrooms. I was a lot easier than i thought it would be.