How can one be happy when they know that their loved ones are engulfed in burning agony in hell? If you were to be happy in heaven, you would have to not be you.
Christians like to say that the whole "burning in hell" stuff is all a metaphor, but if everything that gives Christians an issues is a metaphor, then that gives some credibility issues to everything else.
I suppose the question is one of truth or not. Christians may or may not be happy about the final resting place of their loved ones. But truth is truth. Non-christians may not believe such a situation, but it won't change the truth. They would prefer to think - "gee how do I feel about such a thing" as though one's feelings have anything to do with the truth.
For me the entire point of this universe is to be in a right relationship with the one who created it. If my beloved ones believe the purpose is to live for themselves and to do whatever they want despite the consequences, should I be happy that they end up where they desire or should I be sad that they were wrong in the first place?
Think about Best Korea - on this forum page. he's written numerous posts about how he wants to end up in Hell and how he rejects the God of the Bible. Should I be upset that he gets what he wants or should I be upset that he's wrong?
The truth is the truth. I can't change the truth. I might well be wrong. And I will have to live with that. Do I want everyone else to be sad about that? No. Everyone's tried to change my mind, but at the end of the day, I have made up my mind. And I will end up where I will.
I don't know what heaven is going to be like ABSOLUTELy. But I am not going to use a silly argument about wondering whether I am happy or not, about people who end up in a place - that they could have found out more about but chose not too because they were too arrogant or full of pride to really consider - the implications of their situation and choice - to make me not believe in heaven.
Truth is truth. I'd prefer people to make sensible decisions. But it is still their decision to make. And at the end of the day, what I feel or what I want them to make - is not going to change the truth.