It can depend on how much "resetting" that you want to do...
Take 3 pieces of "steel", and you mount two to a 2x4 using bolts, and leave a gap in between. Then you hang a third piece of steel, painted in a contrasting color, behind the first two. IF they hit the target they get a nice "PING!"...if not, they get a sad "thunk"....
IF you can reset targets, you can do the breaking of clay birds but with water and whole wheat flour, made into a stiff dough, some color added, and then rolled and cut with cookie cutters into shapes that may be dried in the oven. These won't hurt the environment. Just be sure to put a hole in them so they may be suspended by string or a nail.
One variation that doesn't need much "resetting"..., Say you have 20 shooters participating..., so you make targets of clubs and spades. Ten of each, all suspended down range. The shooter approaches the station, and the person running the station allows the shooter to choose one card from a pair held face down...whichever suit is on the chosen card the shooter must shoot one of the same suit targets downrange... IF all of one suit is shot away before the 20th shooter arrives, then dispense with choosing a card and the remaining shooters simply must hit one of the remaining targets...
This also works for teams, one team is spades one is clubs, and each member gets one shot. The team with the most broken targets wins that portion of the shoot....
LD