I don't know your background, so I don't know what kind of weight your advice to them would have, but I'd be careful.
While I generally agree with blackcat's statement that hospice or palliative patients are usually able to have oral intake as desired, there can be other aspects that can make this a significantly bad idea, even if the patient's dying.
In this case, based on the fact that the patient has lung cancer, I'd be thinking about:
- gut involvement, which could mean anything ingested may sit there undigested for prolonged periods of time, contributing to vomiting risk and pain
- esophageal involvement and associated swallowing difficulties, increasing the risk of aspiration
- cerebral involvement, which means the patient isn't able to make informed decisions about the risk of oral intake.
I say this because I've had families tell me how much their loved one wants to eat/drink, despite thie risk, when the person upset about oral intake is the relative/s. It's very difficult to think of food and fluid, which is usually sustaining and is ties with a majority of family and cultural rituals, as hazardous.
Were I advising this family in a non-professional capacity (eg a small group of friends/acquaintances) I'd suggest the family speak about oral intake with the staff. They may be able to explain why they want to withhold food and fluids, and perhaps review the decision if this is a strongly held wish of the patient.
I'd also want to address the issue of sedation - in my experience this has never been a rationale for increasing the dosage, and I'd be more inclined to believe the family have misinterpreted the decision or conflated it with the intake issue.
That's not to say that the family's wrong, but in any case it's a point of concern for them that may be contriuting to a feeling of distrust of the staff.