I'm thinking of scheduling my wedding date for the same day as my adult niece's birthday
Why would you schedule your wedding for that day?
They celebrate their birthdays every five years and having my wedding at this date will be overshadowed by theirs.
You shouldn't disrespect your niece like that. You should plan your wedding on a different day.
All the attention in the family should be on me and my wedding.
That's so selfish of you. You could easily schedule your wedding for any other day in the year. Don't do this to family.