Don't even worry about it. *IF* it comes up, this is an excellent teachable moment for tolerance. Using age-appropriate language and nuance your unique little one understands, I suggest you explain Worship/Religion is a deeply personal choice and, as with all cultures, there are many flavors. Grandma etc. likes hers served in the Catholic way, Cousin Stacey is a Rasta, etc. Muslim friends wear different clothes, etc. But it all for the same thing. Personal belief--or non-belief as is the flavor you refer to which is just as valid as all the other belief systems. Keep it simple, light-handed, and always age-appropriate. You'll all be just fine. Kids are smarter than we can even comprehend. Best of luck to you ...