probably the 2nd best way to re-use any coupons.com is to, as you said, photoshop out the unique barcode and number assigned to a coupon. You could use these coupons as much as you wanted or unless a cashier realizes the code is not there - then they might be on to the shenanigans and not accept it and all the while hopefully not report said user to the store manager (especially if a bunch of these bogus-barcode-less coupons went through one store).
the hands down best way to get a bunch of these legitimate coupons is to go to a computer lab and print them off computer by computer. remember, we don't want to ruin this for us now, and not for in the future when Hasbro may want to do it again.