Raise the pulse and prime the first touch with passing on the move. Keep the pace easy, receive across the body while jogging, and pass gently to your partner's path.
In pairs, jog up a channel about 20 yards long, passing the ball between you on the move, then jog back and repeat. Keep the pace easy and the touch soft, and receive across your body so you can pass without stopping. Build gradually from a jog toward game pace over several lengths.
Fifteen seconds is the realistic budget for explaining anything to a group of seven-year-olds, and every second beyond it is spent losing them. That constraint, rather than any technical consideration, is what should decide the warm-up you choose for young children, and it is why pairs with one ball beats almost every cleverer format available.
The organisation is the whole argument. No grid to mark out, no numbers to remember, no rotation to explain, no queue to form. Point at a partner, hand over a ball, start walking. A coach can have twenty children moving and passing before a more elaborate exercise has finished being described, and the children who would have drifted during the explanation are already involved.
Within that, the technical demands are deliberately small. Pass into your partner's path rather than behind him, so he does not have to stop. Take the first touch across the body while still moving. Keep the pace easy, because this is a warm-up and a pair of seven-year-olds given a ball will turn anything into a race within a minute.
That racing tendency is the failure mode to watch. The exercise stays a warm-up only while somebody is saying so, and the phrase that works is that we are getting warm, not winning anything.
Be honest about the ceiling. This teaches very little. What it does is start a session on time with everybody moving, which for a grassroots coach with twenty minutes of usable attention is worth more than a better drill nobody understands.
Save it to your private drills, then change the animation, adjust positions, swap equipment, or drop it into a session block. Or start from a blank pitch and build your own.