We went up last year and it was a really great weekend. Yep, the kids will be trick or treating. I'm not entirely sure how much candy to tell you to bring. It was pretty busy last year but since we ended up at Two Rivers because mew was full, we only had 13 kids. I think someone last year was saying to expect at least 150 kids, because I remember thinking about that when we were buying candy for the trip (ended up eating most of it ourselves which was fine)
Make sure you take a few pumpkins and some decorations for your site. People get crazy into the decorating thing, and must have brought a couple uhaul trailers to bring all their stuff but it's well worth it when you get to walk around and see all the neat things people have done. The pumpkin carving contest and costume contest are also good fun. (I'd recommend cleaning the guts out of your pumpking at home...it was really cold for the kids hands last year.)
We are planning to be up there again this year. My husband and I were hoping to test out some late season gear since my parents and kids will be in the camper will be there should our preparations not be enough.