are you able to change the exercise goal to a different type of goal, say daily step count?

I am looking to change the type of goals in the fitness app. I am not one who regularly does any formal of exercise but would like to track my daily step count and have that as part of challenges. Also, is there a way to add more than one person to a fitness challenge, I am a family of 4 and would like to have a weekly challenge of the 4 of us.