Many of us have found there "always" seems to be one parent that has a DJ business on the side or full time, trade advertising for DJing usually works great! Even if he is there to provide background music, kids love to dance and it's away for them to break the ice.
I know our middle school has three big field trips that they take in the year, this could be an idea for a "booth" or table for parents to see. They also did a "What to Expect" newsletter for the kids and one for the parents "What WE Expect"...mainly a list of homework, attendance policy,dress codes, and disapline to name a few. Oh YEAH, also a tear off to give they your e-mail address for communtication of homework, grades, concerns, etc. (I LOVE this as my daughter brings me NOTHING and I can e-mail her teachers -or vise versa- and I know about her "F" before she ever tells me!) A few copies of your newsletter or a simple flyer on your PTO's role at the school, teachers (bribe 'em with a lunch for the following week to ensure they show!) there to talk (Ours do a trivia game with the kids and some have prizes and others offer certificates for a no-homework night). Also a showing of the different clubs/afterschool activities would be good!
Most of this is done during registration/ welcome back night....I like the idea of having just a fun night...