My intended one-shot dungeon crawl ended up cancelled tonight as half the group had various real-life crises and could not attend. While disappointed, I decided to make the most of it and spent time preparing for the next Lost Mine of Phandelver session.
We still have at least one character a little too far behind on XP and another whose player cannot attend. It occurred to me that injecting a completely new element such as another small dungeon could help even things out slightly. However, a list of the current hooks and quests instead indicates that the group could instead engage in some exploration and role-playing.
Combat shouldn’t comprise the whole of an RPG, otherwise we could just play Battletech. Occasionally it seems like the game mechanics reward combat over everything else. Experience points and treasure generally come from fighting monsters. But adventures can counterbalance that effect by including quests that require the characters to solve problems using something other than an axe and liberal application of magic missile. The adventure as written does this to an extent already, such as granting XP for dealing with an undead oracle who does not fight.
Factions and secret societies can also help here. If a character belongs to such an organization, they might have received some sort of individual mission that grants some reward. That reward could range from experience to a magic item to a favor that the character can use later. The current Tyranny of Dragons storyline explicitly encourages this.
Hopefully the one-shot group can reassemble in the future. With the impending holidays, regular campaign sessions will probably become even more challenging to schedule.