DCA would definitely be the better choice for a Halloween event (scary-wise) now that I think about it. There're so many endless possibilities there for a PG-13 Scary Farm-like event. Grizzly River Run could easily incorporate scare actors in addition to some pretty gnarly special effects. Imagine an abandoned gold mine filled with the ghosts of miners and some mutant grizzlies affected by the gases used by miners in their exploits. A legitimately scary carnival spook house could make its way into Paradise Pier, and a villain-based World of Color could premiere during every event. The Redwood Creek Challenge Trail could also host a maze in addition to one of the empty sound stages, if not both.
And can you imagine if one half of Hollywood Land was overtaken by public domain silent movie monsters (Nosferatu, Thomas Edison's Frankenstein Monster, the vampire from London After Midnight, etc.) and then the other half was ruled by various fiends from the Twilight Zone? It'd be great to have zombie takeover on Buena Vista Street.