"I would like my son to get some form of movement with his legs, at least I know he is moving his knees and ankles. We have a toy tricycle, but he only sits on it, he cannot put his feet on the pedals without support."
Happy to hear your ideas!
Tetra is a non-profit organization that recruits skilled volunteers to create customized assistive devices for people with physical disabilities. See our instructables group at: http://www.instructables.com/group/tetra/