I think that it would be a good time to explain when you next see her and are in a reasonable frame of mind, that you need to explain that you can no longer be relied upon to come and look after the grandchild that you already have. That the situation at home means that it is more than likely you may have to give more assistance to your husband as his health is now not so good. That you will always want to help where you can but that she should not rely on you as she has previously as you now have more claims on your time at home and that you cannot be sure of availability at specific times. This is definitely true, not an excuse at all, but it also makes clear that no only can you not carry on doing what you already do but certainly can not be relied on for more help than before. This does not alter your daughters right to choose what she wants to do, but does make it clear that you can no longer be expected to be the first port of call for help in the future.
It will be better to think things through and then inform your daughter of your situation. That way she will know the situation and whilst she can make up her mind as to what she wants to do, she knows in advance that she cannot assume that you will provide the support that she has come to expect.
I do feel that our generation had done all their own childcare, and now it seems to be assumed that we will be available to provide free childcare not just for the odd week but on a permanent basis. Whilst we may not look different and are able to do things for the odd day, we no longer feel upto doing things every day. I am now 80 and would still do what I can to help my family out, but definitely am not up to doing as much as I did 10 years ago. You might need to remind them that you are that bit older and not up to doing such a lot these days!!
