So far, the answer to my question is :"No, we haven't."
I **really** want to hear from someone who can say, "Yes, I have, and this is what I found out..."
Now that I've (hopefully) clarified things a bit, I have every intention to use it a whole lot after we retire next spring. 4 person quadricycles that are made in the US are not inexpensive. The 4 adult model at the bottom of this url link starts at $2800.
http://www.internationalsurreyco.com/four-wheel-bikes/surrey-cycles/If I can find a workable cycle for 1/3 to 1/2 the cost, that's the MMM way to do it.
My wife has osteo-arthritis. The last time she fell down she broke both wrists, part of one wrist was pulverized. A fall from a bicycle wouldn't be a nuisance, it might be a life-changing event for the worse.
My daughter has Downs Syndrome. Her life expectancy operating a bicycle on a city street is less than 3 cars passing by.
So, if we're going to get the health and fun benefits of bicycling as a family, we've got to do it a bit differently from most folks. A 4 person quadricycle seems like a good fit for our problem.
I'm interested in getting a bike I can set up with electric assist so as we get older we can still use it. I'll be sixty this fall and my wife is already 70. We aren't spring chickens!