When you need a moment, or thirty of them, go for Lego. Don't just sit them in front of it and expect a miracle. Call it "Lego challenge time!"
I call this taking a plastic cup and filling it with random Lego scooped out of a bin.
Each child has to use only the contents of the cup to create something. Then they must present it to me and explain what it is. After, they are allowed to smash the other guys creation and use that Lego to start the process over again. My kids give me at least half an hour for this activity! Their imagination shines, and sometimes it spurs quite a giggle fit.
Put an end to stepping on hard Lego pieces, with this tidying trick that gets your kids involved.