If you're trying to create a sunnier atmosphere where parents feel welcome and appreciated, start being sunny. Start talking about sunny-ness. If you're trying to foster an atmosphere of involvement, talk openly and often about the help you're receiving and how great your school is.
People follow leaders and are attracted to success. If your group is struggling and you continually share those struggles, then very few people will step up to try to save a sinking ship. But if you can position your group as the place where people (already) are and as the group that's (already) doing great things, your odds of attracting people and doing those things go up.
As we enter our next presidential election cycle, learn from the candidates -- spin, spin, spin. In this case, you'll be doing it for all the right reasons.