RE: cows
Get some coroplast, it is used to make outdoor signs, it is light-weight, waterproof, comes in sheets 24"x36" use 4 or 6mm thickness. Draw out your pattern on the sheets, cut them out & attach them to a frame. Cut out some holes to see through and attach some posts to the legs so you can stick it in th ground, and a couple of handles to the frame so you can carry the cow. Paint the whole thing to match a cow. Just like making a silo.
Hope that helps.