I have two kids both starting at age4 questioned me about death. I don't believe in God so it's hard to calm them, but there is no better way to comfort them, s

I have two kids both starting at age4 questioned me about death. I don't believe in God so it's hard to calm them, but there is no better way to comfort them, so I say we will all go to heaven when we die. One day we visited my grandparents cemetery,my boy started crying, and asked me why my grandparents are buried here while I said people went to heaven when they are dead. I had to say that our body remains here, but our soul/spirit go to heaven and we live there. Then one night he tears again, then cry, when I ask, he said if it's just spirits/souls go to heaven, we won't even have a face there, our family will never be able to recognize each other, and we won't be able to re-unite in heaven. I almost cried myself.