We are also doing that cruise,yesterday (6/6/08),we received a book with all the tours and a price list.They are quite expensive,but it does say how much walking is involved.We are particularly looking forward to a trip on the Flam railway which we will organise ourselves.
I would suggest that you contact the Shore Tours Department at Fred. Olsen Cruise Lines in Ipswich and seak their advice. The number is on the website and in their brochure. You will find them helpful.