Yeah, if a child is curious I will sometimes politely and mildly engage and say something like "It's a power wheelchair. I use it because walking is bad for me." I want to teach children that wheelchairs are normal and not to be afraid of. (After all, some of them will grow up to need one.)

but I've suffered enough rude adults already that rude adults I encounter in the future will not be coddled.

Another time on a train I had a creepy man in his 40s-50s ask in a really nosey way "How long have you been... [trails off, indicating powerchair]"

and I said in my best cross school teacher voice "That's REALLY NONE of your business" and he got all huffy and apologetic, sputtering about how he didn't mean to be rude, He meant well, Wah wah wah, soothe my ruffled feathers, and I just ignored him until I got off the train at the next stop (which was my stop.)