These tips from Lifehacker are great, I wouldn’t have thought to bring bags for the candy or anything like that. Here’s a sample:

“Bring provisions. Take along a few healthy snacks and plenty of water – and be prepared to share with those around you.”

I would also add to the article’s suggestions that you’ll want to bring a blanket, camera (make sure to get the little one’s reactions) and a few band-aids/first-aid items (Lil’ Duck is obsessed with jumping or stepping on and off the curb, and has skinned up his knees and hands before).