Aww, so tragic. Sorry to hear this. I would suggest getting down eye level, and sitting down. Hold the child's hands when you explain it. They went bye-bye to Heaven to be with God. They were in the car and the car crashed and they went bye-bye. They loved you very much, and you'll never be alone because they're now in your heart.
Good luck, and God bless.💗

I guess that would depend on the child not sure anyone can help here so many factors it has to be your call
The way u handle it will be the right way praying for the little soul U got this stay strong my friend