Hi. I'm so sorry to hear that your dad is in this situation.
I am a Community Carer and would agree with your concerns about having his bed in an open plan space.
Sometimes, it's unavoidable & people do cope but if there is a conservatory large enough to accommodate the hospital bed, then I would definitely use that.
To try to put it delicately, bed care will involve your dad being given strip washes in bed, clothing changed in/on the bed and very often (if we are talking about the very end of life), changing of incontinence pads & cleaning him up in regards to that. Obviously, there is a certain smell attached to that - which is not really best placed in the kitchen or even lounge area. Your dad could be rather embarrassed about being the cause of that (I know my dad, who also received bed care with terminal cancer at home, was).
A separate room, with a closable door - even if it's only closed whilst the carers are working - and curtains or blinds would be hugely preferable for maintaining your dad's dignity and comfort. Also, the bed cannot be flat against the wall, as Carers will need to be able to access both sides to give bed care (for rolling, if he is unable to stand mainly but also because H&S rules now state that we cannot bend right across a bed - and actually it's probably not very nice for the person in the bed for that to happen anyway).
Lastly, there will be 'stuff' for your dad that needs to be kept close to hand. A bowl, flannels, towels for his strip wash (once unable to transfer to a bathroom), packets of pads if needed for incontinence at any point (usually delivered monthly in boxes), it would also be useful to have somewhere to keep a few clean clothes & bed sheets handy so that the carers can change him without having to be constantly asking your mum or other family members for things. Also any medical equipment he may need at any point. All of which, makes being in a separate room - where possible - much preferable.
Wishing you and your dad all the best
.