To add a little more to what Cheshire Figment wrote:
The actual distance walked in the Fastpass Line is not much shorter than the regular line.
I would suggest using Fastpass or going in the late afternoon because the wait before the accessible pull off line will be much shorter. The mid-morning wait in the regular line may be 1 hour or more in the morning. When we have gone in the mid afternoon, the trams are pretty much loading from the regular line as fast as people could possibly walk in. Some rows or seats are even empty because people are not walking in fast enough.
People post that the animals are more active in the morning and to go on an early morning safari, but that has not been our experience. When I have gone early, there has been a lot of mist/fog near the ground, which has limited our ability to spot animals. I recently went to the Safari at 3pm (without my DD in her wheelchair). I saw many animals, including both the lion and lioness walking around. The CMs do things to entice the animals to be in the viewing areas, including putting food out for the animals to find in a natural habitat type way.
The entrance to the accessible boarding area is a short distance past the stroller drop off area, so you will be waiting in either the regular line to that point (or the Fastpass line if you have Fastpasses).
If you think she could walk the distance from there to the regular boarding area, you could leave the wheelchair/
ECV there with the strollers and continue on in the line. Anyone using a mobility devices (even walkers) past the stroller drop off area will need to use the accessible boarding point because they cant be put onto the tram and the regular trams board in one spot and unload in another.
Since the regular trams load and unload in different areas, if you leave anything in the stroller parking area, you need to be prepared to walk from the unloading area to the stroller area to pick it up after the ride.
The accessible trams load and unload at the same place and there is space to leave
ECVs, wheelchairs and walkers. The longer wait is partly because of that - you have to wait for guests to get off the tram you will be riding on. Because they have mobility challenges of some type, some take longer to get on and off. The CMs will not begin loading the next group of guests until everyone has gotten off the arriving tram and are leaving the boarding area.
Another reason for the increased wait is that there are less accessible trams. The first accessible tram needs to be past a certain point in the safari before the next one can start. This is for safety reasons in case an evacuation is needed.
How much of an extra wait you will have will depend on how many guests are ahead of you when you leave the non-accessible line and enter the accessible one. You could get lucky and have a short wait because there are few people ahead of you and a tram pulls in just when you arrive. Or, you could find that one is just leaving and there is a tram-load of people ahead of you in the line. The line sometimes goes all the way back from the accessible boarding area to the gate that leads into that area.
There is only one spot on each tram where a wheelchair can be tied down, so someone who needs to stay in their wheelchair will have an extra wait unless everyone ahead of them is able to get out of their wheelchair and get into the ride car. On a recent trip, when we arrived, there was one safari tram full of guest ahead of us already in line, so we had to wait for the next tram. When it arrived, the person ahead of us needed to ride in her wheelchair, so people behind us in line who were able to transfer to the tram went ahead of us and we had to wait for the next tram.
How many are ahead of you in the accessible line is something you wont know until you get there. The only thing I can say for sure about that line is that someone who is able to take a few steps and board the tram will be boarding faster than someone who needs to stay in their wheelchair.