“How should I approach constipation in a 7 year old?”

Increase fiber and reduce dairy products

First, a history of constipation should be obtained. How long, is it intermittent, is it from toilet training (unlikely because of his age), is it behavioral, is it related to his diet, e.g., not enough fruit & veggies in his diet? Rx fruit juices, increased fluids like plain water can help.

If the constipation is new, what has changed in the diet. Is he getting enough vegetables and water? You also can increase fiber which helps stools pass easier. If he needs medication, I use miralax 1 capful in juice daily and it can be given 2 times a day if needed,

Constipation in children is very common. Instead of giving laxatives, I prefer to find why he is constipated. Treating the reason that caused the constipation is better than just giving laxatives. His pediatrician can examine him to rule out any of the following:
-Encopresis (soiling his underwear)
-Habitual constipation (some kids are too lazy to go to the bathroom because they are busy playing)
-Dietary (their diet is low in fiber)
-Anal fissure (a tear in the opening of the anus that can be caused from passing a dry, large, hard stool)
and many other reasons.

You need to identify the reason for the constipation. Sometimes, too much solid food might be the reason and you need to add more water to your diet. A trial of prune juice might help, too.