Kimberly,
We also experience LOTS of attendance at the first and second meetings. This is where we go all out with snacks, ice breaker questions, and sign up sheets for future volunteering opportunities. We also make sure that we appear open to suggestions from anyone and appreciative of their time.
We decided last year that attendance at meetings wasn't as important as volunteering for things. Many people don't care to be part of the planning/deciding process. So early in the year we sent out a form for folks to fill out and indicate which events throughout the year they may be able to help with. I also made note of anyone available during the day.
One key thing with this is to make sure that you actually follow up and call these people even if you are in big need of help. If you don't, the form will become meaningless to them.
However, we also have asked the grade levels at our school (we're a K-8) to send one representative to each meeting. Great way to get teacher input. (Our middle school teachers only have to send one between the 6, 7, 8 grade teachers since there are only 4 altogether.)
Again, don't sweat the lack of attendance at meetings -- things can get decided much more quickly. I would say work on making volunteering a fun, useful, appreciated form of participation.
We often joke at our less-attended meetings that we could always start some sort of controversy and that would get us more attendance!