I have been using an ECV for going on 4 years of going to Disney and I am 28 so the age part, yeah I get some stares but its only people who do not understand what may be wrong with you mostly. I have never had anyone be RUDE to me actually as a "normal" person thank goodness. Just a few flubs on the ride which I will get to in a moment.
I use one also at places like Walmart and the grocery store etc and I dont care if I see someone I know, most just dont even mention it.
Now we go to the crowd factor as I call it. I LOVE Disney as much as the next person but I have noticed the deer in headlight look from a lot of people as they walk around and I just laugh it off. The place is amazing so I give them a little slack in their "lost and dazed" walk. I really do wish people could find a way to look where they walk though and not to their side.
I would tell you first off do NOT worry about people looking at you, trust me, with so many people in carts you are NOT the one they really are looking at. There is so much COOL stuff around to gaze at and even if you are as pretty/handsome as a Hollywood movie star most people are busy looking for Mickey's and/or hidden Mickeys
I have always used the rule of leaving 2 or 3 person lengths in front of me when I drive so that the unexpected stop leaves me room to react. That is only challenged when (usually teenagers I've noticed) will jump in front of you so that they can get through faster. The jumpers will be a problem because as much as I hate it, I have only ever hit ONE person who just did not leave me any room. This woman was in her 80s though and I felt REALLY bad and told her I was so sorry multiple times but I had witnesses who assured me it was not my fault. I thank goodness for people with an outside perspective. She jumped in front of me and then it happened, I only caught the back of her foot before I stopped and she did not fall which I was thankful for. Her husband proceeded to cuss me ought, which is why outside witnesses stepped in to assure it was not done because of me being a reckless driver. I gave you that story to just give you a little of what can happen.
I will assure you that most of the CM for rides will be very happy and understanding, and even though the FAQ says you do not need the GAC, I have been ASKED for it multiple times even while on my scooter before I could pass.
The rides I can tell you from experience that may cause you some stride will be Space Mountain and PoTC. Both of those were not built with an "on stage" access for safe entry with an ECV. You will however be welcome to change to a WC if someone can push you. My problem is I have no one who can push me in and I had to have a CM walk me a much shorter access back stage to PoTC and well Space Mountain they just let me ride the ECV up into the ride but bad news there, there is VERY tight walkways and there is no "way out" that any manager could tell me so I had to have someone escort me down the fast pass line side I came up on. That worked fine till someone with a stroller was coming up and I could NOT let them pass by me because of the small ramp. They had to halt traffic on that side till I got out but it only took about 3-4 mins. Man that was one heck of a trip!
Also the HM ride, they seem to now want you to go through the normal queue then stop at the handicapped banner on a chain. I always used to just enter in the exit side and go in through the "Servants Quarters" then found it it is MUCH easier to just get on the ride at the exit side and you go around to where the other people load on. You even get to go through the "unthemed" back part where most people are already off. That part is fun for me lol.
As for rides, that is about the only extra advice of what usually puts a tiny hitch in the experience for me but everyone else's experience will be different.
I also will make an honorable mention that people with strollers in general and people who let their children walk in front or behind them unwatched will be hard because kids will walk right into your cart if you give them the chance. Since I do not expect kids to know better I stop the art and let them keep walking until they are just about to run into me then make sure they and their parents notice me and what "almost" happened. I do not see this as rude because I do not cause a scene or put down the child or endanger them in any way. I just want the parents to see why its SO important to watch their children! More times than I would like, people with strollers will jump in front like teenagers seem to do.