Confronting the final stages of cancer is always very emotionally difficult for surviving loved ones and all you can do is support your mother emotionally with as much affection and understanding as you can, and hopefully also give her some extra help around the house, as she's probably finding it very difficult to carry on with normal life at the moment. Nobody will be able to prepare your mother for seeing your grandmother in the final stages because, even with strong medication, it is not always pleasant to see. I don't think taking your grandmother on a cruise is really a good idea. She won't be feeling well and if her condition suddenly and quickly deteriorates, as it may well do, there will not be sufficient medical care available to give her the pain relief she might need., as well as all the possible extra stress of getting her home in an emergency, either alive or dead. Probably being supported by Macmillan nurses in the comfort of her own home would be the less stressful environment for your grandmother, and also for your mum too. Just keep up the hugs and the emotional support for both of them.