Things we do at our club:
lay out a rope ladder on the floor and make the kids step between each rung - by having two ladders side by side, it makes it a race. Alternative to rope ladder would be to chalk small square in a line on the road/path. Makes the youngsters take many smaller steps, on their toes, fairly fast so that they don't lose their balance. After going up and down the ladder (i think it has about 20 rungs) a few times, they do 50 yard sprints with the coach or a senior athlete running behind them shouting: 'move, move, move'. As the senior is (a) much bigger than them and (b) faster so he is very close behind, it really makes the kids move. They all have a laugh at the end as the seniors invariably trip up and go flying trying to avoid falling over the kids.
Also: they use a belt with an old car tyre fastened to it on a 15 foot rope. They have to run up and down the car park towing the tyre. When the belt and tyre is removed, the kids positivily bounce round the track.
Could perhaps try putting a rope round the waist of your youngster and holding it so that he has to drag you along.
Also, they do a lot of short 'fartlek' sessions up and down the football pitch - when transferred to the track/road they can run much faster