If a halfling character wanted to cheer up an Angry party member by using their Nature (merrymaking) ability how would that check work?
Would it be something done during the Adventure phase or Camp phase? Both?
How would you determine the Ob of that check?
I would probably restrict it to camp, since players need to have time to take a breath and relax in order to be cheered up. I suppose it could make sense if there was a big lull during the adventure phase it would also be okay, but then the GM probably isn’t pushing hard enough 
Ob 2 or 3? The healer obstacle for overcoming Sick is Ob 4 and Injured is Ob 3 whereas the recovery is Ob 3 and 4 respectively. So it seems like they made Healer a little easier for Injured than recovery, but with the added risk of a really bad condition, and Sick because it’s more difficult with relation to that skill. I don’t think merrymaking would have that same awful failure condition (permenantly lowering will because a halfling made the wrong sort of jest seems a bit harsh), so I would at least make the obstacle the same if not harder than the recovery difficulty. If you were trying to recover from Afraid, I might allow it but I’d make it at least Ob 4 because it’s not as immediately appropriate to the skill.
I agree with jovialbard. It should happen in camp – preferably you want to have a little party, or at least some drink and some songs. The halfling has to be able to make merry! Set the obstacle as you see fit – jovialbard’s suggestion is a good one. I tend to set it based on the number of people participating in the merrymaking. It’s easier to make merry with a group than with just one or two. This means that Merrymaking is great when you’ve got a bunch of angry people in the party!