E.C.
Our church does an annual "Pumpkin Patch" every Halloween in the church gym so the neighborhood kids have a safe alternative to trick or treating - we have a lot of homemade arcade-type games (ring toss, beanbag toss, etc.), simple hot dog dinner and pumpkin pie dessert, and of course way too much candy.
We've also done church/neighborhood bbq's with music and a couple rented bounce houses for the kids.
Another neighborhood church where my kids attend a midweek kids club has "friends day carnivals" 2x a year where the kids are encouraged to bring a friend, and for fun they'll set a goal for X number of total guests and if the goal is met, the youth minister gets a cream pie in the face ;-).