Do you have any advice for potential travellers?
The walking is not particularly challenging and the time allocations in the brochure are generous. The longest walks were about five hours (Etna/Stromboli) and I would have graded them moderate at best in terms of difficulty. They certainly weren't challenging - at least at the pace we tackled them at. On Stromboli in particular a moderately fit walker could have tackled the peak in about half the time allocated.
Both Etna and Stromboli were optional and had specialised guides. They have to cater for a wide variety of abilities which I thought was a bit unfortunate, especially on Stromboli where we were restricted to a glacial walking pace (there were not just Exodus clients in the group) which was very frustrating. Etna was better - the guide was happy to join in running down the mountain (thick volcanic dust) which was great fun.
Everyone was at great pains to warn us of the jellyfish (I began to wonder whether this was a local in-joke). I saw a few, certainly not great blooms of them. I got stung a couple of times. Perhaps I was lucky, but it was at worst a mild tingling - certainly nothing to worry about. Take swimming shoes for the beach - walking on the stones in bare feet is much more uncomfortable!
On the free day most of us took the boat trip. This was a full day trip unlike the optional walk which was a couple of hours. It was well worth it.