ok I have read some of your post here is a few things
1 the parks at disney world are much bigger then disney land ( no I have never been to the land ) but I know a lot of people that have you are criss crossing the parks a lot.
2 FP+ some parks EPCOT you have tired FP so you can not get a FP for soaring test track and illumination all on the same day. I would get a FP for soaring and let your DD do single rider line for TT it is very easy to find a spot to watch illumination about 45 minute before and the rest of the party can take turns walking to what ever country in close by.
Also book your fast pass as early as you can so your time on site 60 days off site 30
as fair as medical if you need to rest first aid is a great place cool some times dark and most of the time quiet ( they do try there best to keep it quiet but some times it is not like when someone is really hurt)
they do have free transportation to and from the ER ( I know you do not want this,) but I am almost sure to urgent care center not sure of other places. I know you will have a car but it is there is you need it like if the rest of your group need to go back home
the only real welcome show is at MK I know EPCOT dose not have one AK they make some announcement and birds flay ( really not that cool)
HS last I remember nothing.
but park oping are great you can get a lot done in the first 60 to 90 minutes
the
DAS is the same as at disney land from what I hear you will need to tell the GR CM why you can not wait in traditional lines you will ( and this depends on who you get ) some want ever one in your party to link there MB or cards some just want the card/ MB
some tips for some rides
MK
7DMT they do have a week chair car where the side opens and you can get in. the ride dose sway back and forth but is kind of smooth.
PP but the line is quite cool so it is just 30 minute you may want to do sand by ( they also can not stop the moving belt)
IASM has a boat of two that you can drive on
JC also has a boat or 2 they you can ride on.
space and BTRR will give you a return time if you go on them.
EPCOT
space ship earth you get on thought the exit they will slow or stop the moving walk way for you to get on
I think figment the sea and living with the land and the mexico all have ride cars you can stay in your wheel chair on
HS
TSMM has a ride car you can stay in your wheel chair I think the great move ride to but not quiet sure.
AK I am not at this park enough to really know
hope some of this helped