A question for Christians about why death is not considered more of a celebration than a tragedy.?

A 2 year old just died in my friend's sister's hot tub a few days ago (they are all devout Christians) and everyone is of course devastated. As an atheist, I understand the devastation, because that is how I would feel if something happened to my daughter... I would know that she is gone from me forever, and that would be unbearable. Christian beliefs however state that the child would go to heaven (which is a perfect place) and that her family will join her there when they die (assuming they Christian as well.) So why so upset? Of course I understand that there would be sadness over missing the child (or whomever the deceased might be), but it seems the sadness outweighs the "reality" of their beliefs. If my daughter was taken from me and put in a place where I knew she would escape all the pain and sadness of this world, and only experience joy while she waited for me to die and join her, I'd miss her for sure, but I think I'd also be happy for her. Any thoughts? Not really looking for a right answer here, just a little insight.