Doesn't look like you're overpacking--personally, I would bring an extra shirt for the adults, and some extra shorts for your son just in case the diaper doesn't do the job, if you know what I mean . Otherwise, you could bring some laundry tabs (or premeasured detergent), a couple of dryer sheets, and some quarters--they don't take up much room--and you'll be prepared to do some laundry if needed.
Where can I find one of these pack lists?? We leave in 3 1/2 weeks and I have not even begun to think about packing due to a bunch of unforeseen craziness happening in our lives right now.
Someone on these boards gave me the tip (months ago) to make a copy of my hopper passes (backside) in case i lose them . The thought of losing my 5 day passes (for four) freaks me out so i'm taking every precaution!! Apparently Disney can track the number and re-issue new ones if this happens.