Hi,
I would certainly do online check-in - it does no harm and might be beneficial.
You go to a 'bag drop' line as opposed to the check-in. This line is right next to the others so you wont have a problem finding it.
The bag drop line is meant to be shorter than the check-in line but to tell you the truth I didn't think there was much in it.
I reckon it is more likely to get the seats reserved online if you check-in (I may be wrong here). It also gives you an hour extra time although we still arrived 3hrs before the flight (but then we would have arrived 4hrs before if we hadn't checked in).
I would also fill in the Advanced Passenger Information online.