it should be other way round

Spend more time in Maui, Oahu just use as arrival and departure points.

Actually you can fly directly to Maui.

Haleakara National Park at Maui is a MUST. Even if you dont go that early to see sunrise, you should still go up there in the morning. (frog rolls in after mid morning and visibility is greatly affected.) The road going up is very scenic. The park itself looks just like the surface of Moon.

There are many other places in Maui that are far more interesting than Oahu.