Hi Graham ... what a sad situation.
I would advise against travelling with just baggage insurance, as the financial implications could be enormous in the event of any illness or accident.
However, with respect, I would also disagree with Miss Pink's opinion that any insurance taken out now would exclude pre-existing conditions. In most (but not all) cases, cover for pre-existing conditions is only excluded if the insured person fails to inform and agree terms with the insurer, and then seeks to make a claim directly or indirectly related to that undisclosed condition.
Page 1 of this topic includes specific recommendations for several companies which provide cover for pre-existing conditions. Entering the word 'cancer' in the search box in the bottom left hand corner of this topic will also retrieve all previous discussion related to insurance cover for that illness.
Some insurers will impose hefty premiums to provide any cover whatsoever, because of the illness and terminal diagnosis. However, some may only impose a hefty excess, in respect only of any claims arising specifically in relation to the disclosed and accepted pre-existing condition.
Unfortunately, it will be a very time consuming process to shop around for the best terms as in situations such as this, online quotes are not possible and you have to telephone the individual company medical pre-screening helplines, details of which will be found on their websites.
I do hope that they can find an affordable policy which provides them with adequate cover.
David