We did this today (And the IOA trick or treating).
IOA Trick or treating you go into the main store at the front of Islands of Adventure "Trading Company" and the kids get a trick or treat bag. There's 1 or 2 gift shops in each land (Other than Hogsmeade) that have pumpkin stickers in the window. Walk in go to the counter, they get candy.
For Scarecrow stalk, you can get the booklet at any shop with the scarecrows. The booklet has a map. Each one is unique to the area (The Transformers one was cool, but each had some flavor). The store clerks stamp it, at the end you go to the Candy Store (Studio sweets or San Fransisco Candy Factory) and if you have everything stamped you get to one of four or 5 different bags of candy. I.e. Candy Corn, Gummy Worms, etc. Stores with it that I can recall is the Minions gift shop, shrek gift shop, transformers gift shop, bourne gift shop, Spongebob store, Mummy Gift Shop, Fast and Furious gift shop, Men in Black Gift Shop and the Irish store next to Louie's pizza. Both IOA and Studios make you go into the various gift shops to get stamped/candy, but it's fun, you don't have to buy anything extra.
I did get a time (somehow) for the Bride of Frankenstein house, and that went pretty well, I actually like the groups being split. Downside is a lot of the curtains, hanging things aren't there, and there's plexiglass covering up some of the areas where actors are. But it's still a haunted house. Hint, Bring DARK sunglasses and wear them in the queue line before going in, then take them off when you walk in.
And yes the parks were very busy today.