I have three boys, 10, 4, and 1. I take the older two by myself at least once if not twice a month to WDW and have no issue. I usually bring a single stroller for the 4 yr old. We also have a double stroller. But, it is the version that is the width of a single stroller and is just extra long. That one we use when we travel as a family with all three boys.
You have to be considerate with your strollers. I can't count the times there is some big nasty double stroller and the parents are acting like they are the only ones on main street stopped right in the middle of traffic. I have also noticed that people in general are more rude now at the parks. All of the self involved me me me stuff. You know the general lack of respect.
I have also been on the end of the rude guests that do not have a stroller and think they own the place and do not make room for others. It really wakes you up when you see the general rudeness towards pregnant women there too. I have witnessed this several times when my wife was pregnant.
I used to be in the camp of parents that would not take their child to Disney until they were 5. Now, though I have a different take on it all. Started taking my 4 year old when he was about 18 months. I don't regret not taking my 5 year old when they were younger though. But, I'm also not going to leave out my other children just because they are not 5 yet. They can still enjoy themselves. Plus you get to witness their joy too as their parents. I mean when you think about it. How many days can you remember perfectly even at age 10 or 20 for that matter.
Disney has great bathrooms for diaper changes. All of the bathrooms that I have been in over the years have a dedicated table built into the wall for diaper changes. Definitely spoils you for when you have to go back out in to the real world and deal with one of those cheap pull-down trays for diaper changes.
