Entertain the kids with their own mouths (and have them learn a little in the process).
Kids like to play with anything at hand and sometimes what is at hand is, well, a face. At some point during childhood, everybody hears the old wives' tale: "don't make that kind of funny face or it will stick that way." Well, these funny faces won't stick, but the educational benefit here just might. If your kids don't know already, list for them all the vowels: A, E, I, O, and U. (Sometimes Y.) Then, you and your kids make the different vowel sounds: an A, an E, an O sound, and so forth. Part of the fun of this activity is looking at how your mouths are shaped for each sound: an O sound, of course, makes a circle of course, but what does an A do? In our house, we think an A stretches your lips, and an E really stretches your mouth!
It's learning and it's fun. And we hope that your kids will say, "Oh, this is A great time. Yip-EE!"