Also, wasn't it largely Zarra who was going to sneak towards the town and meet up with the others or were we going to have most of the group make their way down at some point?
Yep, your right Dai the paladins divine sense, is pretty much limited to fiend, celestial and undead.
Out of which, undead maybe a bit more commonly, encountered. So, if I'm going to use it, at all may as well target that.
Anron, it does not say that you have to choose one of the three types of creatures to target. You will sense any of the three when you activate it.
Another important aspect is that it only lasts a round or so when used, so in the 6-12 second range ('end of your next turn') and you have limited uses per day. It doesn't just stay active all of the time.