the last time i saw my dad on a bike i was looking at his back from the kiddee seat. now he is going on 60, a retired grandparent, and has made a couple comments about going on rides with me. i would like this, but i'm not really sure what he can handle and would like to proceed cautiously. he is no athlete, has had knee and back troubles. i think he rides a stationary bike once in a while. he lives in illinois, pretty flat. comfort and easy to ride are the important things here. i was thinking maybe recumbent, but i don't know anything about balancing them. i was thinking recumbent trike, but now we are talking some serious dough for something that may not work out. any thoughts, bikewise and psychologically, on how to make this happen would be appreciated. i think it would be good for him to get into something and get some exercise.