Certainly declare everything. My problem is I worry in case I've forgotten anything no matter how minor. The other thing with insurance is not just the premium but are the underwriters any good at paying out. Although visited medical facility a couple of times nothing major and not been worthwhile claiming due to premium excess. The last time, DW saw the Doctor on a RCI Transatlantic, he knew our home town as he used to work at one of the local'ish hospitals.
About 8 years age we had to cancel one cruise at the last minute a week before Xmas and we were refunded bar a few hundred pounds by New Years Eve - all done by email. The balance was an error by the insurance company and they cleared that within another few days.