Thanks for the suggestions folks!

I did end up going out to the flask, because it involved interacting with the fewest set pieces along the way. It didn't take very long - just hoped across the river at the crossing near Scratch (pet the good boy), then walked up the high part of the risen road avoiding the other gnolls until I got to the flind, and waypointed back to the grove once I'd done that. Pretty smooth, all told - just one single fight, and no major set pieces to disturb.

I got the weave scene (for the first time.... possibly thinking of doing a breakdown for halflings, but there's not as much to it as I thought, and the bugs can just be submitted into Larian's form, so no point making more issue of it), so, here are a few more data points to help unpack it:

In my game, I was planning on recruiting the boys, so Lae'zel got it into her head that she was going to complete her trial and kill that darned mindflayer if it was the last thing she did. As it turned out, it WAS the last thing she did. She killed the mindflayer after we defeated the commander (so, congrats to her, she's can go home to the astral plane now?), and then the cambions promptly killed her while I took care of the transponder.

I recruited Gale first, then spoke to him - no probing, just asking his questions, then immediately rested. This was the first camp, and nothing happened. Because of that, I wandered up the road a bit, checked on the area where Lae'zel would have been, and was disappointed to find that the two tieflings weren't even there, and then rested again: this triggered the "Go to Hell" scene.

After this, I went and picked up Astarion, and rested again; this triggered the "Mirror Image" scene, and Astarion wandering away.

I rested a couple more times while moving about the areas, but didn't approach the grove yet. I went to the ruins, and convinced Gimblebock to leave (+ Gale Approval), rested (nothing), and then cleared out the ruins - Gale got most of the lore dialogues as we went through. I also allowed Gale to get himself killed during this part, so that I could do his protocol. I spoke to him about it, but didn't press the issue, and said he'd tell me when he was ready (+ Gale approval). Rested again, spoke to him in camp about his protocol, but didn't push it (he's jovial about it, and admits that at very least, it piqued my curiosity) but no further events yet.

I went to the grove and did the fight at the gate, then settled things between Aradin and Zevlor peacefully (Halfling dialogue, then easy persuade) (+Gale Approval). Because I didn't want to miss it and hadn't seen it before now (ever... I only know about it from one of my partners...), I ran down to the inner grove and gave Volo an interview (Silly man ^.^), as well as paying my respects to Kanon - his sister ran off to threaten Sazza, but I didn't follow. Continued to ignore conspicuous Shadowheart placement and immediate availability of magic items all being very clearly designed for Shadowheart...

Rested in the grove, and this now triggered the "I Trust You" scene with Gale - every time previously, I've only had this scene trigger when I got an artifact he could eat, so it was in fact a novelty to me to get this scene before I had anything to feed him! I agreed to help him, and was a good sport about it - my new character for this run is not really a material kind of person anyway, and she's not the very bright either - just good-natured, helpful and optimistic. Gale was Neutral before the trust scene, but was at Medium after it.

I recruited Wyll now, but didn't exhaust his dialogues - most of them get a response "maybe when I trust you more" or "only my good friends get to know that", but then they don't reappear later.. so I'm leaving them until he's in high rep, to see if he says something different. Rested, but no new scenes.

I then hiked out towards the flask. Stopped at the boar, then rested, got Astarion's scene, and in the morning opted for the "We need him" line; saying that you trust him gets a negative from Gale, so I avoided that.

Continued hike towards flask, but was stopped again by True Soul and co. I sent the kids away to the owlbear, then crushed the tadpole (+ Gale Approval), then because I felt guilty, I rested (nothing new), then went to the owlbear cave and followed the siblings inside. I crept past them, engaged with the owlbear, noticed the cub, then peacefully backed off (+ Gale Approval), and then told the siblings to leave - which gave me a hint about the goblin camp.

Continued hike towards flask - but stopped to pet Scratch and take good care of him. Good Scratch. Pat-pat.

Hiked out the rest of the way to the Flind, dealt with that encounter, then spoke to the Zents as a well-meaning and helpful person with no guile at all. Astarion, being much more profit-minded, crept behind them, picked the chest, looted the flask and then crept out again while they weren't looking. We said goodbye and went on our way.

I chatted to Gale here and now and fed him the flask, then rested. This triggered the "Weave" scene. Before the scene, Gale was on Medium approval, but was on High approval after it. I suggested romance in the scene, and he was receptive, and I think that's all the boxes marked for romance at the camp once the grove is saved.