A few more things
Toss in a couple of those metal tubes that you can tape over broken tent poles to splint them. We brought a little black light flashlight to look for scorpions on one of ours and it was fun. Think about renting a sat-phone. Tunes and a little solar charger? Throw in some little toys, little action figures, cars, and some string to have an awards night late in the trip: best rescue, best run, worst run, best meal, etc. Spare sleeping bag, bivy bag if someone loses a tent. Think about a theme night and bring an outfit: Luau Night, Movie Night, that sort of thing. November? Bring a Mr. Heater & extra 20# propane. I could go on and on...