I just saw a videothat is part of a video series about death entitled For Those Left Behind, by ustaz Omar Suleiman from the Yaqeen Institute (https://yaqeeninstitute.org/watch/series). This particular episode (https://yaqeeninstitute.org/omar-suleiman/ep-11-losing-a-child-for-those-left-behind) talks specifically about parents losing a child.
Briefly, few points from the video:
1. Losing a child is a unique tragedy. For parents, having to grieve for a dead child is one of the heaviest and greatest trial in life.
2. All children are pure, and they will definitely enter Jannah. They will also wait for their parents at the gates of Paradise. This is true whether they are children of believers or non -believers, whether they died after having lived for awhile, or miscarried as fetuses.
That is why, it was mentioned in the video, that we do not have to worry for the children that have died, for they are pure, and they are definite dwellers of the Paradise. It is us, the adults that are left behind that need to live on with the pain. And if we were to do it right, the way Allah intend us too, we will meet our dead children in Paradise as well.
3. The prophet himself, Muhammad (pbuh) lost 6 of his 7 children! And still, he himself cried, despite knowing about Allah's promise of what happens to these children in the hereafter, despite him already being able to see and smell Paradise with Allah's will.
It is okay therefore, to be sad, to cry, to grieve. It is okay to acknowledge this great pain, as long as we accept the loss humbly and be thankful always to the Almighty for it. Allah has promised us the rewards - protection from the hellfire, and chance of seeing the children again in Paradise. We just need to make sure we continue to strive for it, insyaAllah.
Subhanallah!