Let us terrorize the Grand Line!
I feel like they'd want to do Reverse Mountain. But it looks like, according to the Calm Belt page on One Piece Wiki, that Amazon Lily is close to the edge of one of the belts. Maybe we can use that to have them sail out into the sea, then head downwards to enter the Grand Line via Reverse Mountain. But that method of island hoping sounds good to me. Until we decide to do an "arc" and give them a destination/throw in some drama.
Haki it is then!