My son started pin trading at Aulani. He found the nicest pins at the more upscale gift shop, but that may have been chance? The DVC salesperson by the pools also had pins to trade. There are some really fun Aulani specific pins.
Be aware the pin trading is just a bit different at Aulani than what you see at Walt Disney World. Unlike at WDW, there are very few Cast Members at Aulani who wear lanyards with pins on display; the exception is the CMs who work at the DVC Preview Center just off the Aulani lobby. At Aulani, pin trading binders are available for the asking at the General Store, Concierge, the Community Hall, among others.