The beauty part of going to Hong Kong-style electric cars isn't the lack of fumes, it's the sound!
To passers-by, the electric karts are near-silent.
To the little passengers inside, they don't sound like lawn mowers anymore, but like real race cars, thanks to the onboard vehicle audio and a small subwoofer in the seat. If they wanted to get fancy, they could have different cars with different engine sounds, sports cars, muscle cars, or as in Hong Kong, futuristic vehicles, so that different vehicles would yield different experiences.
This, plus a little more landscaping could really plus the attraction and eliminate most of the complaints against it.