This is one of the few events that does allow candy to be thrown from the vehicles. There are kids (big and small) along the entire two mile route. Almost every one of them has a candy sack waiting to be filled. The best purchase is the large generic bags of candy from Wally world. You can get by with one but with multiple throwers you may want more.
All the parades that are in our area do allow passengers in the cargo bed. Just make sure you have plenty of water/food as the wait time and drive time will take a toll. There are restroom facilities at the meeting point.
Looking forward to meeting you.
And yes flags a decorations are required equipment