One of my favorite props to use with newborns and other small children is mirrors. I haven't met a little one yet, who doesn't love to smile at themselves in the mirror. It gives them an opportunity to play, and you are still getting the fabulous pictures you want.
Shooting with mirrors can be tricky, since the only reflection you want in the picture is the subjects. I tend to shoot these pictures on a slight angle, so I don't show up behind them.
For small children, I either prop the mirror up and sit them right in front of it, or I lay the mirror flat on the ground and have them lay on their stomach, their elbows resting on the edge of the mirror.