I don't think there is anything you can say that would be uplifting. These people lost their young son. They find comfort in believing that he will be resurrected "perfect" in mind and body and walking with them in the future.
Similarly, there is the reply from another lady that expresses her & her children's belief that they will play hockey together "in heaven".
Do you think it's better that you (or anyone) awaken them to the fact that there will be no resurrection, or there is no "heaven", or anything else beyond NOW -- other than DEATH?
If one of my children or grandchildren were to die unexpectedly ahead of my own death, I'd damn well wish that I again had the certainty that there was more for them somewhere/sometime. I would love to know that some Supreme, All-Wise Being is "going to fix it all" in his own due time. But I have come to the point in my cynical life that I only accept hard evidence. No more fairy tales and false promises.
Don't be a shit-disturber. Let them have some peace.