Some parents commit more time than others. Several parents do just show up at meetings, although they love as much involvement as possible.
My husband ended up being the leader in the second year and it was a lot of work. On the other hand, he, and by default my son, ended up with a tremondous amount of respect from the other parents and children.
Even if you cannot commit much time, do not let this discourage you from joining. It has been a wonderful experience on so many levels. It also provided some bonding time for my husband and son.