Another

here. I always used it with my 2 kids because all 3of us wouldn't fit in a typical stall and I didn't want to leave one out by themselves. I just let people go ahead of me when I got to the front of the line until it opened.
Another thought is the family bathrooms outside, they have the bars too I believe.
To add to what other posters wrote;
When people hear/read 'family bathrooms' they generally are thinking of restrooms set up for families to use, with changing tables and possibly even small, child size toilets.
That is not what Disney parks have; they have Companion Restrooms, which are set up to meet the guidelines for ADA handicapped accessible bathrooms.
Many of them do not have a changing table. None of them have lower toilets. All of them have raised seat toilets with grab bars.
There are only a few in each park (5-6) and they are the only toilets in the park that some people are able to use.
We generally use them as much as possible because my DD is in a wheelchair, her wheelchair does not fit in some of the handicapped stalls, we need a sink in the stall with us and she has sensory issues that can make being in a busy bathroom difficult.
Most people are nice, but in the past few years, we have sometimes been treated very rudely by entitled families - for example, as we waited in line for the Companion Restroom, I have been told, 'this is for families. You people have stalls in all the restrooms. Go use one of those.'
We have had people bang on the door (not just knock), and someone once called Security to tell us to get out because they needed the changing table. I had told the people the first time they knocked that I was in there with a disabled person and would be about 15 minutes. After talking to me through the door, the Security CM asked if they knew I was in there with a disabled person; they said they did, but felt I was 'taking too long' and they needed to use
that restroom to use the changing table. The CM explained there are changing tables in every restroom, but the people said they needed
that one. What was really funny was that Companion Restroom did not have a changing table.
So, if it's busy, with lots of families, we sometimes use only the Companion Restroom in First Aid because we know no one is going to bother us.
Everyone pretty much spelled out HA stall etiquette as I have also experienced it. When you enter a theme park, you can get a Park Brochure for the Disabled. It shows which restrooms also have a separate family restroom. The family restroom may help you, with your child, to have space and privacy. I think I remember last time at MK, I had to go to City Hall (inside entrance, to the left) to get the "Disabled" brochure.
The guide maps for guests with disabilities are available from Guest Relations, but also can be found in the park map kiosks with all the other maps. They are labeled for guests with disabilities and have a black band across the top of the map.