I suggest you put in some long trainng sessions over the next two weeks. These sessions should be 10-12 hours long in the best case. It is hard to do workouts that long day after day, but that is the key. You need 10-12 hours a night of sleep. A week of that and you will be fine. These sessions work best with a training partner, definitely not your son.

Pneumonia recovery is very fast, but you need to get sleep. This is from a person who at the age of one was not supposed to survive the night, but who was playing in his room with 48 hours later as if nothing happened.

Your son will definitely find running with you to be boring, but that shouldn't happen for a year or two anyway.