I would recommend you come to the Blue Lagoon directly from the airport if your flight arrives at 7,8,9 in the morning. Hotel Check-in is not until 3pm and this place will relax your mind a body from the over night flight.
Obviously you'll have to time it right, but if you're up for it, this place makes for a great destination wedding! They even have a chapel here that's been blessed by the local parish. Given the changing nature of the hotel, however, don't expect it to look exactly the same from year to year.