There are treat trails spread out throughout the park where you can get candy (for free). They will give you a treat bag to start with but they are pretty small and fill up fast. We bring gallon ziploc bags to dump the candy in and carry them in a backpack
They will give you another bag if you fill the first one, just ask at the treat stations.
My wife and I filled 3 bags and now have enough to give away at Halloween. ha