A themed event is one way to make a mega open house inviting and successfully bring out people from your neighborhood. This is especially a good idea around the holidays.
Also, you can consider these ideas that are sure to draw a crowd:
Lemonade or hot chocolate bar with baked goods
Burger bar
Pop-up shops with local artisans
Tour of new home decor trends
Incentivizing with a raffle or major giveaway
Wine tasting event