I share my birthday with Benjamin!
Both of us had pretty much equally represented birthdays, don't worry. We celebrated my birthday first, right after I loaded up the game. Bianca came over and was like I have a surprise for you and so she took me to her house. Benjamin was there with Whitney and we all celebrated my birthday. They gave me a present and I made a wish.
Then after that was done, I went out and walked over to Benjamin's house next door. He was there with Frita, we celebrated his birthday by me giving him a present and he stayed inside all day like you'd normally see with villager birthdays. Villagers throughout the day would sometimes mention my birthday and ask what my wish was, and of course you'd see the bulletin board mention congratulations to both of us.
It's really cute

hope you have as good a time as me. Idk how your day would work completely though since it's also the harvest festival/thanksgiving that day. But it's probably gonna be something similar. At least you'll have lots to do that day