Footwork is very important. I would say it is even more important if your kid is a "he". All the top ATP guys do have "pristine" footwork.
The earlier your player realizes how important it is and work hard on it, the higher level he/she will achieve. Many parents new to tennis are so concerned with their kids's strokes and spend little time on footwork. Without proper footwork, kids are not going to hit quality strokes and will not reach their full potential.
I would suggest 2 things that can help tennis specific foot work.
One is to practice shadow movement without hitting the balls. Watch the Bailey Method video above. It might look a little silly but have your son practice those shadow moves and recover before start hitting the balls. Another suggestion is to hand feed the balls to different spots on court. Without good footwork and recovery, he is not going to hit those balls right. I found these 2 things helpful and improved my daughter's footwork a lot. Hope these will help your son too.