Decided to store them in the sphere, which was a good thing because I had to fetch the sewer key. Mind flayers are horrible to fight, but at least Korgan (with his +10 intelligence) was able to handle them better than the dumbwitted Minsc.
You could also put them on the ground. I am not entirely sure, but I *think* quest items won't disappear like other items eventually do.
By coincidence, I found out this is correct. Went back into Mae Var's old place, and saw a quest item where the barkeep once stood. Must be weeks ago in game-time, so quest items probably don't get deleted, even if you leave them on the ground.
Another question. I've not sided with Bodhi before, but did now. I'm evil after all. She said something about trading opportunities inside, but I can't find anybody useful in there at all. I've been all over her little crib (including downstairs), but only find lemmings and Bodhi, and we're about to board the boat now. Isn't it possible to trade there after all?
Oh yes, one more thing. Once inside, I picked up the Mace of Disruption +1, and saw on some BG related site that we need illithium to upgrade it. We have already completed the Sir Sarles quest, so he grabbed all the illithium. Is it impossible to upgrade the mace now? It would have been a nice niche weapon.