I'm so sorry that your mum is dying and some of the responses on this thread, it's actually upset me as I've cared for someone in this situation, two people in fact, and it's just so awful and hard and if I'd got replies like this I would have been very distressed.
In my husband's case, there was no option to come home, he need a team of 2/3 to move him and toilet him, so once he'd moved from home care to the hospice that was that. The hospice won't allow people to go home without the correct equipment, support and trained carers, you can't just take people out and let the fall over which is very likely if you don't have the training to transfer or the equipment at home. The chances of getting carers in at short notice is nil, it takes ages to be accepted by Macmillan/charities for someone sitting with you (plus they don't do actual hands-on care in the one we had) and all the agencies I know are short-staffed.
It must be very traumatic to go and stay in your dying mum's house and to suggest you are going for a holiday, well, it's just such an awful thing to say. What you are thinking about, which is utterly correct IMO is how you can combine this trip with looking after your 5 year old so she's happy, occupied and not traumatized. Many terminally ill people look very scary, and seeing her in a nice hospital and having a cup of tea might be very different from you trying to care for her, wipe her down, change her clothes, the smells etc in her old home if it's not set up well and you don't have other carers. I would ask the hospice about taking your five-year-old in and when's best, they are usually fantastic and used to the whole family visiting. Or even leave your child behind if that's a possibility.
It sounds like she wants to do something, so maybe a short visit, or even sitting in the garden of the hospice or hospital, having a cream tea, take the things she can eat- I would talk honestly about the prognosis of the hospice and ask them for help to help your mum in her final weeks to make her happy, explain what she's said and get their advice.