Jim, While I am inclined to believe that a trike would be an improvement over a bicycle for a person in your situation, I would incourage you to consider the 'bent version. I have had episodes of vertigo in the past and I don't think that I would have done all that well on the trike that I own. The biggest problem would be in managing the corners. One must make sudden changes in the body position to corner and to dodge unexpected potholes for example. If one's balance is off or disturbed by these motions then an accident could occur. Just my opinion as an experienced trike rider.
Paul Patzkowsky