Okay, most islands in Thunderhead are very high up, and the Bug Island (or whatever it's called) is located on the left side pretty far in I believe. You could think it's at 10 or 11 o clock when you enter from the larger part of the Sky. It's hard to describe.
Perhaps left of the Isle of Songs is a better description.
I tend to love the 3D Mario games for stationary systems, which are Super Mario 64, Super Mario Sunshine, Super Mario Galaxy and Super Mario Galaxy 2. I've also tried many different 2D side scroller Mario games, but it's occurred to me that I'm not at all god at side scrollers, and because of that I don't like the 2D Mario games that much. Anyway, SMG2 is by far my favourite Mario game, I think it's as good as any Zelda game and I've beaten the game 100% three times.
And good luck proceeding in the dungeon!