Cabbage and others,
Have you read
The Selfish Pig's Guide To Caring: How to cope with the emotional and practical aspects of caring for someone: Hugh Marriott
Really worthwhile. It discusses the sorts of things people feel they can't discuss.
I hate to say it, but simply driving down every weekend to keep an eye on my parents when my father was terminally ill four years ago left me exhausted. I ended up getting run down and it took months to get over. I therefore leapt at the chance of voluntary redundancy (public sector cuts) a couple of years back, knowing work, kids and mother was one juggle too far. Part of the package was a career interview. The advice was strongly not to seek other employment whilst there was a crisis looming.
In my case my mother is wealthy. I even feel guilty writing this, but as a POA I charge, albeit reasonably modest amounts. Her first idea was to use a solicitor who would have charged a fortune, so she is much better off paying me. I did it, not so much for the money, but to help reduce potential resentment I might feel, given the bulk of the burden has landed to me. I did not see why I should also be the one to have to pick up costs (petrol etc) and suffer loss of earnings, as well as committing time and energy. My mother understood. The argument that worked for her, was that I needed to contribute something to my family who had lost out as I was effectively absent for 3 months. She is very much part of the generation who believes a wife's duty includes having a meal on the table each evening. To her it was astonishing that my husband had allowed me to prioritise her needs over his, and had been willing to take over caring for the kids. At the back of her mind, I suspect, was a fear that he might put his foot down.
I found it difficult to be assertive especially in a family context. Everyone's circumstances are different, but you are right to look ahead and to consider what boundaries you need to set, in order to achieve the solution that works best for everyone. I could not have made it work if I was trying to balance with f/t work or if I was seething with resentment.