The simple entrance makes it easier to deal with, so that's good.
Start from the standpoint of taking a basic side step in closed position. Strong compression into right leg to provide support for a good sized side step. Here's the important part: As the side step is being taken, avoid *any* hints of sway, rotation, or body shapes. Move the entire body as one unit, solid as a rock, with hips straight and level.
After weight has been fully established over the left foot, then start to work on the shape. There are two primary elements to this shape: (1) Rightward rotation, and (2) Leftward sway.
The rightward rotation takes place in the torso and hips. There should be no mis-shaping of the arms; this is entirely body rotation. Be careful not to pull back on the right side (this can affect the lady's balance and/or break the dance position). Instead, project the left side forward.
The leftward sway is all hips, baby. The right hip should be higher than the left hip, plain and simple. The man should watch out that he doesn't exaggerate this sway with his top... if anything, he should be stretching his left side long, not dipping it down. Also, even though the lady may be looking to the right, she should still work on keeping the head *weight* over her left side, just as she does in promenade position.
Try to hit on all of these points with the kids, but the most important thing to remember is: Have them dance completely through the side step, with weight fully transferred, before beginning to take to the shape. They may blend it when it comes time to dance with music, but for learning purposes, it really helps to break the movement up clearly.
Good luck.
Sincerely,
Jonathan Atkinson