99% of people using ECV's at WDW have "hidden disabilities"; you can't tell just by looking at them why they use an ECV.
Think of it like this - the ECV is a TOOL, and nothing more. The eyeglasses that I use? A tool - to help me see better. I'll bet you have used a calculator at least once in your life... that is a TOOL to help with math. (I stink at math, so I always have a calculator handy). These are all tools that people use every day. So, an ECV is also a tool for humans who have trouble walking/standing. It's about using the tools that are available - and appropriate - to make the most of your time at Disney World.
You aren't using the ECV in any way that is inappropriate. You have a legitimate need.
I promise you - you may be feeling very sensitive about using an ECV at WDW, and you may think that folks are upset/glaring at you/making remarks. A few might, but overall, people are increasingly so very self-absorbed at WDW that you on an ECV is simply a non-event. In fact, you will need to watch out while driving your ECV! People at WDW (and everywhere, really - let's be honest) are often so self-absorbed in their phones, conversations, surroundings, etc. that they will WALK RIGHT IN FRONT OF YOU. While you are moving! Mostly when they aren't busy running INTO you, or BUMPING you. It happens on a startlingly regular basis. Your most effective "weapon" is a bright smile, and a pleasant "Pardon me!". Just remember that it is NOT intentional - they just aren't paying attention to their surroundings. Just try not to run over them if possible LOL!
We were just at the parks in February of this year. At that time, strollers outnumbered
ECVs by a fair bit, and our daughter (whose 21st birthday we were celebrating) noticed that it was just "easier" to use the ECV at the parks. People seemed MUCH more accepting of it, and even more helpful at times (holding doors, etc.) It was, overall, the easiest trip I ever had using an ECV.
So my advice to you? Get on that ECV and ride. Smile & wave at everyone, and make eye contact. Don't worry about what anyone else thinks; the chances that you will see ANYONE from Disney World outside of your trip ever again? You have better odds betting on the lottery. You stand a better chance of getting struck by lightning! Your odds of winning the lottery AND get struck by lightning in the same day are better! You will NEVER see those people at Disney World again, in all likelihood. So don't worry about them. They are all too busy worrying about themselves, and taking "selfies" and posting pictures of their lunch on Instagram anyway.
Have fun, and may you have the most Magical trip yet!