yeah, there are a lot of discrepancies like that...but in the end, so what? it doesn't really change all that much, and besides, a suspension of disbelief is a necessity when it comes to literature, no?
"Don Corleone, I am honored and grateful that you have invited me to your daughter... 's wedding... on the day of your daughter's wedding. And I hope their first child be a masculine child. I pledge my ever-ending loyalty."
