Kallang Leisure park is ideal. Not too much people (that we end up blocking the public) . Near MRT. Mall for drinking coffee later. If really keen still can adjourn to nearby scenic point to test out the new UWA that we just bought, too.
How about the open carpark near scape? There's a good crowd there and the carpark is not always full. It's in a central location, and even passers-by will come in to look around.
If we're only going to be there for one day, worrying about the businesses there is being a little it too considerate. You're worried about Kaypoh people? They're everywhere!
For me, the more central the better. I live in the west, so will not go all the way to kallang.