Recently I saw an online comment that made me scratch my head. The poster was stating his wishes for a departed friend. He said something along the lines, "I don't believe in God, but just in case there is a heaven, I hope ...." He then went on to state how is friend might find joy in heaven.
If you don't believe in God, I would presume you don't believe in Heaven. But if you allow that Heaven might be a reality, by extension you allow that God might also be a reality. If wish for a friend to find a joyful Heaven, you must actually believe in God, despite your claims to the contrary.
Years ago I had a similar exchange with a coworker, also an atheist, who had a friend going through serious health issues. She called me one day and asked, "I know you are a faithful person, so would you please pray for my friend?"
I thought, if you don't believe that God exists, why would you think that my prayers to Him would help your friend?
I offered those prayers nonetheless.