If trading with the elves, remember to un-assign any wooden buckets for trading before entering the trade screen.
Not necessary, unless you're afraid you'll mis-select. They don't complain about forbidden goods (or containers) so long as you don't offer them.
(Last trade with the elves I did, last night, had wooden bins with mixed wooden/non-wooden items in them, plus loose wooden furniture that I'd added to the [PENDING] queue to finesse a movement of the items to nearer where I wanted them (also, likely going to be at zero distance when I select them for trading with the Dorf traders), via the ultra-high-priority Trade Goods hauling that overrides pretty much all the other jobs. I didn't detrade anything, after they'd arrived, just carefully stepped across wooden things when marking my offered stone goods. They certainly didn't add anything wood to the list when I'd made a stingy offering, but then they had plenty of non-wood to choose from all the while.
Maybe if you're on the edge of "can't fathom you with all those items" they might
try to select things they wouldn't accept, first, but I've not seen that happen and would assume they'd self-censor their own suggested additions rather than end up insulting themselves.)
An aside from the original question, but might be useful to know in this situation, anyway