Set up in 2's with 1 bat and a ball.
The aim here is to keep the ball up in the air by hitting it lightly with the bat. If the ball hits the ground it becomes your partner's turn.
Shake hands grip on the bat should be encouraged.
Try holding each end of the bat.
Set a target for your players to aim for (5 keepy ups for example). Increase this as the players become more proficient.