I went with a trike. No balance issues. You can go slow without falling over. You can stop without falling over.
Angle Lake has a broad selection of quality trikes and a big parking lot for the initial Does It Fit Me test. Worth a stop. I switched from my MTB to a trike and am very pleased with the change. No more discomfort. No more chamois, creams, powders, etc., etc. I can ride all day in comfort.
A good starter trike is the Terratrike Rover or Rambler. If the knees are getting iffy, the Rover seat is the same height as a folding chair. I have one iffy knee and no issue from trike riding.
Of course, a senior Roadie will pin to keep up with the boys. Trikes are said to be slower up hill and faster down hill than road bikes. That said, I am quite happy with my HP Velotechnik Scorpion FS.
<http://www.utahtrikes.com/HP.html>
As mentioned - read the mail over at BentRiderOnLine: Trikes.