A few years ago, my wife and I did a supported tour of the Aland Islands - phenomenal flat cycling. I did a CycleBlaze journal
here.
We pretty much did what the previous post recommended - island hopped and took the ferry back from Marienhamn. The route was did would easily be doable unsupported, from a food/lodging point of view - the towns are not very far apart - assuming everything is open. We chatted with many doing it camping vs. lodging.