I ran across this fun tandem trike trailer today doing a web search:
http://www.twoplustwo.uk.com/tbikes/bb04.html
However, according to the company they are currently changing their name from 2 plus 2 to Bike HOD and no longer are making those dual pedal (tandem) trailer bikes.
I can't seem to find a link to the Adam's tandem trailer bike. Does anyone know if they still make it? I found links to four single trailer bikes they make. And I found a link with a picture of the Adams "Ultimate Tandem" for 2 children, but don't know if they still make it.
http://www.electric-bikes.com/trailers.htm
BB