First thing to do is ditch the electrical tape for anything other than holding the covers on or adding decorations. It just doesn't stick well and it gets much worse if there are temperature fluctuations.

Gather your materials and bring them out to the park so there is someone else to help with the first arrow you make.

At minimum you will need...

• Duct Tape
• Strapping Tape (has fiberglass or nylon filaments running the length of the tape, if you can't find any I will have some with me)
• Closed cell foam (camp pad, packing foam, the cylinders you mention might work but I would like to see them first)
• Stretchy and/or light fabric for cover (Lycra/spandex works very well as do trouser socks)
• Arrow shafts
• Something to blunt the tips (typically people use a penny or washers to screw into the end of the shaft, your blunts will probably work)
• Some sort of glue/cement for fixing the blunts into place. (I will have some with me)
• Stress Balls (I'll be bringing some of these out as well)