Get an ECV. DO NOT FEEL BAD ABOUT IT. You can park it and stand in lines or wander around the park walking if you want and then return and use the ECV when you're tired. The old system that gave people with wheelchairs access to shorter lines is long gone. There are special wheelchair return times for ques that can't accommodate wheelchairs/ECVs, this means you request a wheelchair return time from a CM outside the ride and they will give you a time to return to the attraction based off the current wait time. You don't need a disabled pass to use wheelchair return times. You wait as much time as other people so you aren't taking anything away from average visitors or taking anything away from someone more disabled than you. If you want to stand in the line and not use the return time pass you can! Just park the ECV outside the ride and walk right into line. Please don't feel guilty renting an ECV, there are lots of ECV rental options in the area that deliver to hotels and Disney rents out ECVs at the parks. (I wouldn't do a wheelchair as that can be exhausting to push around if you, or those in your party, are not used to it.)
I'm really trying to get you to reconsider the ECV as I had a family member with similar issues, they could walk but had serious standing issues. When they finally relented to an ECV it made our Disneyland trip SO MUCH better. The family member had a much less physically taxing trip and the rest of us had a much more relaxed trip. I don't know if you're travelling with others but we didn't realize how much time the rest of us spent worrying about our family member and their physical issues until he got the ECV. It was this huge weight of worry and stress off our shoulders that we didn't even know was there.

to the DISboards btw!