To the OP -
I would get together with the other parents who also brought pot-luck dishes. Those folks are the class act of this bunch. Hang out with them, maybe even when the season isn't on...they sound decent/nice...everthing the exclusionary/stand-offish people aren't.
Don't bother with the clique, they really aren't worth it. My DD talks about the popular girls (she's in middle school). I always tell her "Wait a minute. These girls are *NOT* popular. They are not the nicest or most well-liked AT ALL. They are simply the girls who decided to seize power and wield it. Call them The Clique if you wish, but do not EVER call them "popular."
And if you and the other Nice People hang together, you will have more power within the team parents and the more you might be able to affect positive change. (And you might be able to actually enjoy yourself.)
agnes!
PS - These women sound like they ARE stuck in high-school. You might want to read a book called "Queen Bees and Wanna-Bes"...I understand it describes how girls behave(and how some women continue to behave) to a T.