Iceland in 6 days

We will be in iceland from June 14-19 with two young teenage boys. Our plan is to rent a car and do the following: Day 1- chill in Reykjavik during day, thermal pools, wander;leave kids with pizza at apartment and go pub crawl (Friday night) Day 2- get 4x4 and drive to Landmannlaguar ,hike, bathe then drive towards vik for night Day 3- explore south coast somewhere run Reykjavik Day 4-celebrate National Day in Reykjavik somehow Day 5- golden Circle Day 6- blue lagoon and environs, afternoon flight. Any advice? Car rental suggestions? Lava tubes to explore without hiring a tour company? Thanks