I like both names Finn and Sawyer, but can see the dilemma. My son's name is August and although I like the name January for a girl, I obviously could never use it because although we like both names independently, it'd be too calendar-y to have two children named after months. So our daughter's name is Martha and another girl due in a few weeks to be named Hazel.
That being said, I think that naming two children in a family after months of a year is obvious while two literary characters, although well known, seems more subtle. And as for kids in school...I don't see it being an issue.
It if truly is your favorite name, I'd go with it. Childhood is a short time in a person's life...and then they'll be independent adults with a long future...and with good names.
I wish you the best for a healthy remainder of your pregnancy and delivery!