In my experience, the survey results won't be earth-shattering. You'll probably find that many of the same people who already volunteer and attend meetings are the most likely to respond to your survey. Maybe you'll get a couple of new ideas that make a difference. That's good stuff.
But the real power comes from the fact that you're asking -- and so making it clear that you seek and value all input. That's a message you want to send frequently, and it's a message that does wonders for your efforts to involve more parents. If in doubt, ask for the feedback. You may be scared of what you'll hear, but trust me, the results are worth it.
We have some great survey and feedback resources for you: