We bring a picnic blanket that zips up neatly (picture somewhat flat square). This packs easily into our suitcase and we bring it into the parks for a place to sit and wait for fireworks and Fantasmic. We have young kids who are usually tired by then, so we don't mind finding a spot and waiting, but a blanket is a must have! The kids will even lay down for while. Or sit and play cards or their DS's while we wait.
So I guess you can add cards (regular and/or Uno) to our list of random things we bring
Also on this note, we are currently on the lookout for a mini flashlight lantern to have just enough light for the kids to see to play the cards after dark.
Last year in Nov, two girls were playing cards beside us waiting for F! and it got too dark for them to see, so my kids offered to hold one of our mini flashlights on the cards for them to play, which was sweet, but not feasible to sit and hold a tiny flashlight for that long, which made me think a mini lantern style would work great, it doesn't need to light up a large area.
I know this seems like a lot, but really, waiting for upwards of 1.5 hours is a long time for children to sit still with nothing to do.
I should note, that I am referring to F! at
Disneyland, although this link is on the WDW side, I love to come here for these tips that are really helpful for both parks

I believe the seating is different for F! at WDW, where at DLR you just find a spot on the ground to wait, no seating or bleachers.