So many gifts in such brief time. Do you maybe have something to make up for, Fredius?
No, really, many thanks for having unveiled a part of this arcane riddle! Yes, the Goblins are not capable of coping with daylight. It would have thus been more reasonable, if they had tried to violate the borders of Lórien during the night, as it happens in the books (if I'm not wrong) and as that mysterious image from that even more mysterious LOTR art-book, which I remember reading in elementary school, showed. The whole idea of that assault provides the sequence with a substantially different tone, and it strengthens the role of the sentinels of those borders at the same time.
As I previously wrote, though, the scene makes the arrival of the Fellowship in Lothlórien much more dynamic and I think this fact could have eventually altered the pace of the film (considering that the journey in Moria is the apex of action by definition). Again, a nocturnal intrusion (while the Fellowship is resting in Caras Galadhon) would have done better, in my own opinion.
Let's maintain the anticipation and desire for the Misty Mountains well alive!