Different cruise, but we went on the Northern Lights cruise in March, booked several trips through FOCL. As it turned out we could not dock in Bodo (sadly bad weather conditions) and as we had booked a tour to the Saltraumen maelstrom and sea eagles through FOCL we were immediately reimbursed. We also got insurance cover for missed ports so were compensated financially for this (though would still have far rather done the excursion). With hindsight it's probably a bit risky booking independently (though it appears cheaper, which is very annoying). However, in Tromso, a couple we shared a dinner table with had booked Independently a cycling trip - this was successful for them. FOCL never really seem to publish times in port (as you say a bit vague) and I would be nervous of booking something unless I was absolutely certain of the times.