It’s going to come across incompletely any time we talk to children. It should. What can we convey to them as very small ones? That’s all we should tell them. It’s like sex: you don’t need some big conversation, just answer each question, simply, as it comes up and they will accumulate all over time.
As for what you wrote: No, we do not “experience death.” We leave, move on, go elsewhere. We don’t die. Ever. No one dies. We experience change. And Purgatory is so much better than this place, you’ll think it is heaven.
When your earthly life ends, you’ve experienced death. Your life is changed, not ended, yes, but the earthly phase is ended for good. Besides, your body is going to rise again, too.
***CCC 1013 **Death is the end of man’s earthly pilgrimage, of the time of grace and mercy which God offers him so as to work out his earthly life in keeping with the divine plan, and to decide his ultimate destiny. When “the single course of our earthly life” is completed,584 we shall not return to other earthly lives: "It is appointed for men to die once."585 There is no “reincarnation” after death.
CCC 1014 The Church encourages us to prepare ourselves for the hour of our death. In the litany of the saints, for instance, she has us pray: “From a sudden and unforeseen death, deliver us, O Lord”;586 to ask the Mother of God to intercede for us “at the hour of our death” in the Hail Mary; and to entrust ourselves to St. Joseph, the patron of a happy death.
Every action of yours, every thought, should be those of one who expects to die before the day is out. Death would have no great terrors for you if you had a quiet conscience … Then why not keep clear of sin instead of running away from death? If you aren’t fit to face death today, it’s very unlikely you will be tomorrow …587
Praised are you, my Lord, for our sister bodily Death,
from whom no living man can escape.
Woe on those who will die in mortal sin!
Blessed are they who will be found in your most holy will,
for the second death will not harm them.588*
No, there don’t need to be big conversations. What we do say does need to be the truth. When the Church says, “It is appointed for men to die once”, we ought not say “no one dies.” Yes, we do. Death isn’t the nihilistic end that those with no faith think it is, but death is real, and unless we’re among those chosen to be here for the Second Coming, we’re all going to go through it. I’d call that an “experience”.
That’s just it: some people (I do not mean you) do not answer the question when it comes up. Rather, they do everything possible to avoid the questions. They don’t take children around people who are going to die, they don’t talk about people who have died, they don’t talk about pets that have died, they don’t take children to funerals, they don’t teach children to pray for the dead. They avoid avoid avoid, they say “they are not emotionally ready” and then when someone dies who is so close to the child that death can no longer be hidden, the poor child is smacked with some of the most difficult realities of death with no preparation at all. Then they talk about the dead going straight to Heaven as if there is no need for a person to prepare himself or herself for death at all. That’s easier to think about,
but it isn’t true.
My children have had to go through having those very close to them die, and I was glad to have talked to them about it. We did leave truths beyond their ability to process for later, but we didn’t avoid the topic. That is important.