I believe this argument is invalid for the following reasons:
1. It’s Heaven for God and he knows exactly what’s happening on earth.
2. It’s Heaven for the angels and they know what’s happening on earth.
3. Angels in Heaven see the torment of hell, but it does not minimize Heaven (Rev. 14:10).
4. Abraham and Lazarus saw the rich man’s agonies in hell, but it did not cause Heaven to cease to be Heaven (Luke 16:23-26). If one can see people in hell without ruining Heaven, surely nothing he could see on earth could ruin it. This passage shows a chasm those in Heaven and hell can’t cross, but they can still see what is happening in the other place (Luke 16:23-26). If this is true of Heaven and hell, is the same true of Heaven and earth? (And hell and earth?) Is there a chasm separating them and preventing direct intervention, yet an ability to see what’s happening in the other world? (Note: Luke 16 is in the intermediate state, before the end of the world and the resurrection. It does not therefore prove those in the New Heaven and Earth will be able to see into the eternal lake of fire. It seems likely they will not. However, it suggests those currently in Heaven may be able to see into hell—at very least they are fully aware of its existence.)
5. The promise of no more tears or crying is after the end of the world, after the Great White Throne judgment, after “the old order of things has passed away” and there’s no more suffering on earth (Rev. 21:1-4). This passage is not a valid argument for tearlessness in the present Heaven, but only in the New Heaven and Earth. This doesn’t mean those presently in Heaven must be unaware of what’s happening on earth. Certainly those in Heaven are not frail beings whose joy can be maintained only by sheer ignorance of what is going on in the universe. In fact, even if our knowledge did produce some sadness in Heaven (we don’t know for sure it would), the old order hasn’t yet passed away. Heaven is not in its final state. We should not begin by defining Heaven as “no sorrow, no concern, no knowledge of suffering” and then dismiss any scriptural indications that undermine that assumption.
Christ grieved for people on earth (Matt. 23:37-39; John 11:33-36). Does he no longer do so because he’s in Heaven? Or does he still hurt for his people when they suffer? Acts 9:4-5 gives a clear answer. Jesus asked, “Saul, Saul, why do you persecute me?” When Saul asked who he was, he replied, “I am Jesus, whom you are persecuting.” Doesn’t being persecuted with them suggest he’s currently hurting for his people? If Jesus can hurt for them, couldn’t those in Heaven do so also? It’s one thing to no longer cry because there’s nothing left to cry about. It’s something else to no longer cry when there’s ongoing suffering on earth. Going into the presence of Christ surely does not make us less compassionate, but more. Hence, it is possible that even with the predominant joy presently in Heaven, in light of the fact there is still so much evil and pain in the universe, there could be periodic expressions of sadness in Heaven until the evil and pain are permanently gone in Revelation 21.
6. Since God is continuously at work on earth, observing saints would have a great deal to praise him for, including people’s spiritual transformations (Luke 15:7,10). If there is rejoicing in Heaven about what happens on earth, aren’t the redeemed allowed to participate in the rejoicing? How could they participate unless aware of the cause for celebration?
Conclusion: Happiness in Heaven is based not on ignorance, but on perspective. We will be with Christ, see accurately, and live in a sinless environment. Heavenly happiness cannot be based on a fundamental ignorance of what is happening on earth or even in hell.
For more information on the subject of Heaven, see Randy Alcorn’s book Heaven.