I'm returning my MiniPRO

[MacJeepster]

A few weeks ago I bought a Ninebot MinPRO and I've been practicing in empty parking lots because I planned to use it around people since I don't walk very well. Yesterday, I felt confident enough to start riding on the sidewalk in my neighborhood.
It didn't go well.
May of the sidewalk blocks are uneven, and when I went slowly over them, I pitched forward and back. Finally, it pitched me off and I came crashing down to the concrete - my first fall.
I've lost confidence in it; I feel the wheels are just too small.
Amazon has agreed to take it back and refund all my money. They've even given me a label and will pay for shipping. (Yay Amazon!).
I haven't given up, though.
I now plan to get a scooter with larger wheels. I assume that larger wheels mean more stability, but also more weight (I have to lift this out of my trunk and lug it up a half-flight of stairs in my house).
I'm considering:
-An Airwheel S3,
-An Airwheel S5, or
-A used full-size Segway.
It would be very grateful for your opinion or any experience you would share with any of these.
Thanks in advance.
-MacJeepster