This is one I have done many times with smaller children.  Make 2 large puzzles out of card or thin wood by copying a picture off a puzzle or copying your own, stick the picture to card/wood and cut into puzzle pieces.  Colour/Paint the back of each puzzle a different colour.  For the game, split the children into 2 teams and give them one of the colours for the puzzle. Hide the pieces around the rooms, garden etc. Ask the teams to find the pieces of puzzle for their corresponding colours and make the puzzle.  The first team to finish making the puzzle is the winner. You can give the team a prize at the end if you wish.