FYI, I was at DLR on the opening day of Halloween decor last year and it was a bit crazy near HMH, as a dozen (or so?) radio stations had booths set up right there to broadcast live. Plus the FP line and regular lines were so backed up we were right up against some of the booths. Still, it was exciting to be there on the first official day!
SMGG was initially down multiple times during that first day on Friday, the opening day and I couldn't get FP initially. At one point I think I had run back and forth to check on it 2 or 3 times before I finally got on Friday. The agony of it was that I had 3 FP as DH and DD5 weren't going to ride on it and I didn't get to use all of them because of the breakdowns that day. Still, it was AWESOME to ride SMGG twice in a row on Magic Morning because there weren't any people in line after me.
Have fun!