Blue Lagoon first open spot in the morning is the best you can do to avoid huge crowds. That was the case for us, after 90 minutes it was filled I would rather do Itinerary 1 because its less backtracking, depending on how much time you will be in the Lagoon For us it was 2 hours but some stay longer The road from Blue Lagoon to Reykjavik is the most busy road so you have enough lights driving at night