As @
JonathanGennick suggestests, the crank forward bikes are worth looking at, or even a class called semi-recumbent bikes which are a bit lower. A bit different beasts, but you might find them comfortable.
For experienced cyclists, the upright trikes can be a bit disconcerting as they don't lean like a normal bike leans, and they have a reputation for being unstable with high speed turns. Most of them are also 1 speed or 3 speed.
There are two styles of recumbent trikes that can be a blast to ride. The lowest and probably most stable are the tadpole trikes, two wheels in front, one in the rear. These usually have multi gears, and are very nice riding machines, albeit a little low to the ground. Get good mirrors, lights, and maybe a flag.
The other style of recumbent has one front wheel and two rear wheels. Not as low for getting on/off, but perhaps a mix of costs/benefits.
The trikes can be a lot of fun, but I'm not sure I'd be so quick to give up the upright bikes.
Perhaps get some good knee and elbow pads, and of course a helmet, and go to a deserted shopping mall parking lot and practice riding, stopping, turning, slaloms, etc. Balance is always better when moving at a pretty good clip than going slowly.
Also, try some less busy off street bike paths and parks.