Yes there is a small area of wheelchair seating in the front row unless they have done away with it. We've been seated there several times before hearing became and issue and I had to resort to reflective captioning.
We sat there once and as far as I know it is still there. There are only a few spots, so unless you get there first someone else will get those seats.
You are very likely to get wet in those front row seats because the movies are projected onto screens made of water mist.
The night we were there with DD in her wheelchair, it was a pretty calm night (no wind) and we just got a light misting. One time when DH and I sat in the front row without having DD along, it was pretty windy and we got quite wet from the wind blowing the mist at us. There are CMs selling large beach towels in the front 1/4 of the amphitheater. We could not figure out why until we sat there.
The theater is much wider than it is deep, so the back row is not as far away from the stage as you might think. As other mentioned, the wheelchair seating in the back row allows you to see an overview of the whole show. We noticed when we sat up in front that we only really saw what was in front of us.
It is a long distance from the stroller parking area to the seating area, so I would not suggest doing that unless she can walk well for a distance of at least 1/2 block or so. Also, as you come in, the CMs direct people to sit in specific areas. If they are seating in the far left middle section when you come in, that's where you will be directed. If she is at all unsteady on her feet, keep in mind that there will be a slowly moving crowd being directed to the same area you are being directed too. If she comes in with the wheelchair, the CMs will direct her to the handicapped rows. If she doesn't want to sit
right in the back row, the 2 rows in front of that row are also handicapped and we have seen people drive to the area with a wheelchair or
ECV, get out and walk down a few rows, then the CM parks the wheelchair/ECV.
Another thing you could do (which we have done with large groups) is have a few people sit with the person using the wheelchair and the rest get seats where they want (a wheelchair party is usually considered to be a total of 5 plus the person using the wheelchair). Since you already know the wheelchair seating is in the back row, it's pretty easy to 'hook up' with people after the show.