The pawn shop and chili cook off both sound excellent. This is slightly simpler in scale, and might work best paired with something like the pawn shop.
Name of the Event: The Feast of Maximum Occupancy (yes, it's from the show)
Main Quest Summary: Provides players with the opportunity to unlock new squares of land.
Special Currency: Squares of Land
How to earn prizes?: Upon update, 8 or so new quest lines trigger (or however many it takes to make a new strip of land). For each quest line that players are able to engage in and complete within the length of the event, they unlock a new square of land (if they've maxed out), or else gain a square nearest their existing space, plus the potential to unlock an additional square later for the value of the gained space (if they haven't yet).
Prizes: Land
New Features: Land