I will be traveling with a young man whose balance isn't great ~ subsequent to an accident. At home he rides a recumbant 3-wheel bike. Are there options available to rent in Amsterdam? Even a bicycle "built for 2" would probably work...
check out mac bike (http://www.macbike.nl). I rented my bike somewhere else, but mac seems to have a bunch of different bikes available.
There is a shop in Amsterdam that used to rent the Hase Kettwiesel : Ligfietswinkel.
Now their website just says that they rent trikes so you may need to contract them. I see that they carry Hase, HP Velotechnik and Optima. All of these manufactures make or made recumbent trikes.
Thank you for the information! I'll contact both.