Here is a game that exercises your mind. You can make up a word if you're in a bind.
Write at least 20 words on little slips of paper. Fold the pieces of paper, put them into a hat, and mix them up.
Have all the children sit in a circle.
Have one of the children pick a word from the hat. That child says the word out loud and then each child has to come up with a word that rhymes with the word that was originally pulled out of the hat. Children can make up words if they are stuck. The round ends as soon as a child repeats a word already said or is completely stumped.