This is sorta, lowkey, maybe, important;

Your writing style.

Now it may seem like a minor thing, but it can actually be really important.

If you write in the diary entery style, you have to write in past tense. So they must have to survive it all to be able to write it; unless you have a huge plot twist and Daryl or Carl ends up writing the last entry...

But even then you have to change you language choice to fit their characters, which can be reasonably difficult.

So be careful if you do decide to shift things up a bit.