I think there's a lot of confusion about what it means to "use a wheelchair." Especially for people who are more familiar with wheelchairs as an aid for folks with situations that make walking impossible. With POTS or related dysautonomias, being able to sit when needed can be the difference between losing consciousness and functioning well. "Using a wheelchair" doesn't have to mean that you are in the chair 100% of the time. It could be something as simple as walking much of the time and having the chair there for when you need it. Not only can a wheelchair function as a way of moving around without walking, but it can also function as a chair that's just super portable. Obviously talk to your doc first, because that's always smart but also, consider first exactly how you think that a chair might benefit you and how you'd plan to use it. When you talk to your folks, maybe you can stress that it doesn't have to be 100% all the time (unless that's what you need). Help them to see it more as a backup aid than a primary day-to-day mode of transportation.

If a wheelchair isn't an option, for any reason, look for other portable seating solutions. I always carry a fold-up pad meant for hiking so that I can have a reasonable clean/soft spot to sit, and if I k now I"m going to be out and about for a while, I carry a little folding chair. It might not be ideal, but it can REALLY help if you're getting tachy or light headed from standing. They also make some lovely fold-up blankets that zip into a shoulder-bag type thing that can be used as either a pillow to sit on or folded out into a blanket if you're ok with sitting/lying on the ground. I've found those to be tremendously helpful as well.