Sir Wolf,
you wouldn't believe what can be made with a couple sterilite trash cans, elmer's glue, and eva foam and foamies. If you have the time, it'd be a great project for you and your son. Let me know if this is something that interests you. I have a lot of experience with it, and I can help steer you to the right resources.
Beyond that, just scale the armor pieces with the stencils, and then cut it out, shape it up (heat gun works great), and the big key is tricks with krylon paints, and BINGO, ya got some great plastic armour.
YIS
B. Patricius