If this is something that is looked at to be implemented my feedback is to not include Adults by default, only as an option, although if there are options placed on this doesn’t that take away from the “simple” aspect of it, I would not want any adults on the Simple Sign In Sheet as it could get way to long.
There is the option of the Attendance Sheet which gives you much more control over what you see and who is on it. With the added information it is many more pages but might be an alternative.