I like using advantage over static mods to rolls. Your list of daily set up looks good. I'm going to have the party leader also set up marching formations for each type of area (narrow, standard, and wide). I don't really need the navigation checks due to an underdark ranger in the party.
Choosing between advantage and +5 is an art.
Where the adventurers can earn advantage on the roll, you would ideally want to choose +5, so their efforts can be rewarded (instead of "we already got advantage, so no point in making the extra effort"). Where there is no common source of advantage to be had, you can base your choice on other factors: such as "what do I like best" or "matching similar checks already described by the rules".
I know the module generalizes areas into narrow, standard or wide, but personally I think more variety is needed to convey the utter dissarray of Underdark passages. I think I'll use three d6 to inspire me when describing any random encounter, where the idea is to focus not on cold hard numbers such as "width" or "height", but on much more subjective parameters:
the experience.
White d6: the "difficult trek die", a roll of 1 means a perfectly smooth dungeon corridor, a roll of 6 means a very rough going among rubble with several hard climbs and terrifying descents.
Red d6: the "claustrophobia die", a roll of 1 means large airy caverns - the Underdark equivalent of a four-star hotel room ;-), while a roll of 6 indicates low crawlspaces, disgusting lichen and creepy-crawlies, ominous rumbling, bad stale air, and even water-filled sections.
Yellow d6: the "exotism die", a roll of 1 means regular D&D caves: browns, greys, the odd skeleton; a roll of 6 means the most beautiful caverns from the real world dialled up to eleven, with bizarre fungus formations, sickly colors and lights, perverse tinkling sounds, faerzness wild magic, and what not.
When the dice indicates low numbers, that's a good place to allow "easy" Survival checks for food and drink: DC 10.
Where the dice indicates high numbers, I'll place the "difficult" foraging spots (DC 20). On the other hand, it's where the going get exotic you have the best opportunities to harvest those Underdark fungi.
Noone else finds something missing or wrong about the daily check list...?
