[Radek]

Rataxes' advice is the best. Do all three dungeons before you enter the Drow City. You will have as much time for the quests as you want and all quest items (and other special items) will be there even without having any quest. Now, enter the Drow City and store the quest items somewhere in a chest (several chests are on the market place of the city).
Once you enter the Drow City, most of events are timed. When you get the Mother Ardulace quest, you will be able to take the wanted item from your chest and finish the quest immediately.
If you have lost this possibility then try Beholder Lair. It's a difficult dungeon but, as it has been noted above, the Eye is at the very beginning of the dungeon. Catch the eye, leave the lair, and complete the quest. Return to investigate the lair later.