What an AWESOME trip! There is NO better way to experience the island. We loved van life for 11 days for our honeymoon and it was the most incredible experience.
The van has a few quirks, like hanging up the shades every night with tiny magnets... that can be a task, but overall its simple and the luxury of having a car and all your things with you wherever you go is wonderful. Patrick is great and we appreciated his help with everything.
Because we were living rather nomadically, we met a ton of people around the island and made some forever friends. Some of those friends suggested everyone who visits, go to Iolani Palace... and you really should. It's an incredible learning experience and will make your trip so much more meaningful to learn about the islands' history.
If you rent the Lebowski, go in with an open mind. Every experience will be more meaningful because you aren't looking something up or on your phone, or watching tv in a room, or even showering like a normal person... that alone is a hilarious event and just so free and fun. My suggestion, just go with the flow, travel wherever and experience the island for what it is. It's the best way to see Oahu.