A little too simplistic for me
"Father's Promise" was the first TWoM DLC that I played. The premise of being a father having to take care of his sick daughter was an interesting one. Sadly, I felt rather underwhelmed by this DLC. Playing "Fading Embers" afterwards further highlighted the downfalls of FP because FE was so much better.
Like other people have mentioned, there's not much survival mechanics in it because the story is so short that by the time you've set up a good base, it ends. Which would be fine if the story was well fleshed-out, but it's not, really. It's intended to be a tearjerker, but it's very simplistic in the way it achieves this. TWoM sometimes has a tendency towards this, taking a very obvious approach to their moral lessons to the point where it sometimes feels like the game is taking your hand and pointing out: "This is sad! Feel sad, player!"
Usually, it's not so bad that it feels TOO overt, and of course the subject matter usually is very sad, but FP tips over that line (in my opinion). It took a very simple and obvious approach to its storyline, which I was a bit disappointed by.
There's also no multiple endings or any kind of divergent pathways. The story is very linear.
I much prefer "Fading Embers" due to its more complex approach to the moral questions of its storyline, and its branching pathways/multiple endings, so my suggestion is to buy that instead as it's definitely worth the slightly higher price over "Father's Promise".