I understand how it feels.

Frequent use of Ventolin points to the fact that the asthma is not well controlled. Ventolin is just a reliever drug during attacks, but an important part of the treatment of asthma is the use of controller drugs which he can get on prescription.

So, I would advice that he visits a doctor who will keep the symptoms under control. He will give him some controller drugs like low dose steroids, long acting beta 2 agonists and others. And also monitor his lung function so as to step up or step down the medication till a perfect control is achieved. By that, he will not have to use the Ventolin frequently.

On the children,
Cough is a symptom of asthma but it occurs with wheezing and chest tightness. So just cough alone and malaria is not likely associated with asthma.

What may show that the children may have asthma is when they have hyper responsiveness or over reaction to some allergens. Asthma is associated with atopy state which is excessive body reaction to some things that usually don't cause reaction for others.

Some of those associated reactions are food allergy, body rashes, or frequent running nose and red eyes. Those are the ones that show a higher chance of having asthma in the children. But ordinary cough without associated chest tighteness and wheezing is not a risk factor.