I haven't read the book in a couple of decades, but I believe there are several references to Atticus being significantly older than most other guys with little kids, and how this is strange for Scout. When I did the crappy Christopher Sergel version years ago, our Atticus was probably around 60 as well. Probably older than what Harper Lee intended, but whatever. As far as this production goes, they needed a famous person in the role, and Jeff Daniels will sell tickets. However, I remember that when doing the Sergel version, I found Atticus to be a surprisingly boring role. I hope they make him more than just Human Perfection Personified in this version, although I guess that is kinda the point of the character.
I'm also curious how this "white savior" story will play in 2018. Racism has evolved to a much more dormant and subversive form - it's no longer Atticus Finch (the good guys, not racist) versus Bob Ewell (the bad guys, blatantly racist). People are far more complex than that.