Hi and

to disABILITIES!
If you click on where it says "disABILTIES" at the top of this page it will take you to the Index. One of the top items is the "disABILTIES FAQ" which will gives lots of useful information. Post #6 deals extensively with the GAC.
Or, if you want an easier route, click on the link in my signature.
Almost all the WDW queues are mainstreamed, so a person in an
ECV will generally stay inline with everyone else. On those attractions where there is a separate entrance, you would be directed to that entrance.
As Chruchy said, you would not need an GAC as the ECV is sufficient for your needs, but it would be a good idea to get a GAC for your daughter as her needs are clearly different than yours.
And, as a side note, remember that she cannot ride on an ECV with you; that is a severe safety violation.