Having positions is good, even if only good practice
for how things
will be when you're incorporated. A chair should be a person who is
organized and who can can lead meetings and keep them on track. A vice
chair can step in to oversee meetings if the chair is missing. A
secretary will be responsible for ensuring things like meeting
transcripts are posted publicly, and ensuring that the board is in
good communication with the community. Treasurer isn't needed till you
have money, but again, it's good practice and you are going to need
somebody eventually.
Not being professional or focused at this stage will only hurt the
chapter in the long run. I suggest everybody take this stuff very
seriously.
I'm not sure a vice chair is really necessary for such a small board.
I would just decide that in the absence of the chair, the secretary
chairs meetings, and in the absence of both, the treasurer does. In
the absence of all 3, there is barely a quorum, so hopefully that
won't happen too much, if it does the 2 people left can decide between
themselves or just toss a coin - chairing a meeting of two people
isn't a lot of work!