I relate to this very much. I'm a big gal, both vertically and horizontally. Even after many years of using an ECV at WDW (I was diagnosed with Lupus in 1995, which makes walking or standing for extended periods impossible for me no matter what size I am), I still have to fight off the occasional feelings of self-consciousness. I know for an absolute fact that many people when they look at me, and particularly my size, and assume I'm just too fat and lazy to walk like everybody else. Daily I have to just remind myself that it's MY vacation, I spent a small fortune to be there, and I have every right in enjoy myself without pain or misery. That I should pity those small-minded, ignorant people who are so lacking in compassion and grace. I hold my head up high, smile like a goof, and HAVE FUN. And you should too. I know it's easier said than done, but please don't allow yourself to be held back by the uninformed opinions of sad people who you'll never see again... Don't give them the power to make you endure one moment of suffering. ENJOY YOUR VACATION!
Additionally, I notice you say you prefer to drive rather than use the busses so you don't have to risk standing. If you rent your ECV from off-property, you'll not only be able to use it at your resort (which in and of itself can be a whole lot of walking), but your bus problems will be solved as well. You'll be the first one on the bus, so grabbing a seat is easy breezy. You can also do what I do, and opt to stay on your ECV for the bus ride. I like to do that just to free up one additional bus seat for somebody else... No reason to take a seat if I brought by own.
Like you mentioned, I too don't stay sat in mine 24/7 in the parks. I am up and off of it all through-out the day. Anything I have a FastPass for or that has a posted Standby wait time of 20 minutes or less, I just park near the strollers or the attraction exit, and go through as normal. If I decide that I'll need my ECV for the attraction queue, I always just ask the CM at the front what to do, and follow their instructions. I never take the ECV into close quarters like shops or restaurants, I do both of those on my feet.
So by the end of the day, my pain levels are still high, but I stick it out. At least I'm there and able to enjoy myself, where as I wouldn't be able to do it at all without the ECV to help me cut down on the walking and standing as much as possible.
Also keep in mind that depending on how big you are, you may need to be conscious of the
ECVs weight limits. Standard models are built for usually 300-325 pounds. (I think this is the limit for the ones that Disney rents for day-use in the parks, maybe somebody can correct me if I'm wrong.) When you rent from off-property, you can get a model that allows up to 500lbs. As for me, at a svelte 340lbs, I'm just a tad over the limit for a Standard model, so I go for the larger one. I use
Buena Vista Scooters, and they are absolutely wonderful.
Feel free to PM me if you have any questions, I am more than happy to assist in anyway that I can. Most importantly, please try to relax and take care of yourself first!!!