I'm going to be doing this again today
First time, I used a bounced flash on the hotshoe with a 16mm lens. The hotshoe flash has to have lots of power behind it or it will create a large shadow right in front of the camera. That lens created way too much distortion if not corrected.
Today, I will try:
18-55 kit lens for versatility
Flash on a tripod, at a low height, with mini-softbox diffuser
Try to balance the ambient light with the fill from that flash
Most likely fire the flash into the room directly
I would agree with your assessment so far, although 28mm might not be wide enough (most realtors seem to be using a 10-20 or 12-24 lens these days). You'll just have to include more shots using the 28mm which is never bad

I will try shooting on one knee and see how that goes...