Jevs - it's reassuring that you do it from Austraila!
Roseaster - the stroller helped a lot on our last trip when he was 5. We did Universal when he was 6 for two trips (10 days total) and he did fine without the stroller. I figure it will be easier on me not to have to worry about folding our bulky stroller and parking it. (Or retrieving it. I've found parking it is a lot easier than retrieving it). The 13 year old is very responsible usually. But, the last time I told him to watch his little brother while I took his sister to the bathroom, the 7 year old went missing. (He got scared and ran and hid. Luckily, it was in a small museum). Bribery can help the 7 year old at times, so that's in my plans. It cannot help the 10 year old though. I'll try giving her a job though. She might like the map job. She's on medication now and wasn't the last trip so hopefully it will be easier than last time. (Plus she's gone through four therapists since then and one may have even helped her some).
I wish I could count on others to be helpful. There were some people who tried to help. But the rude looks and even direct negative comments I was given due to my children struggling were plentiful.
Ok. If the 7 year old responds to bribery, that might help LOL. I would also set a very firm rule with the 7 year old in that he must be holding your hand or the 13 year old's hand at all times when not on a ride or in a show.
I totally get you about the strollers. I am one of the few here on this board who want to dump stroller use ASAP. I've always found them more of a hindrance than a help.
I think giving the 10 year old a job is a good idea. Let her handle the map, and/or the WDW app. Let her check wait times and such. Maybe it will distract her.
I'm not terribly helpful as, even though I have a lot of kids, I don't have any with any type of sensory or anxiety issues. I just try to keep them corralled. It's like herding cats.
When they were younger I found matching or same colored t-shirts a help. Easier to find 5 purple shirts at once. (My 6th is still a baby) We also "counted off" before we moved on to another attraction.
We also had an all-in rule when they were little (the 1st 5 are 10-18 now) in that where one went, they all went. One person needed to go to the bathroom, everyone went.
I would still do a lot of planning. Buy one of the Disney for kids books for the 10 year old. Let her look at videos of the parks and the attractions so that she is prepared for what to expect. Is she able to verbalize when she is becoming more anxious? Maybe having a way to let you know when she is becoming overwhelmed so that you can take a break?
Go slow. Plan to take breaks and down time. Try to find quieter places to sit and have a snack. Try to find places to have meals that may not be crazy busy or loud so that you can relax and regroup. Follow their cues. If they need to sleep in don't be commando about getting to rope drop. If they are tired or overwhelmed, be ready to call it a day, or head back to the room for a nap.
I found that when my kids were getting to be a bit much we did some of the slower, quieter things. TTA, a monorail ride, Hall of Presidents Tom Sawyer's Island, the train, Living with the Land, the boat ride in Mexico.