So very sorry for you OP
I went through this with my Nana last year. We had 4 days at home before she died.
Definitely make sure you have plenty of pads and any medicines. If you haven't already, speak to the hospital or her GP about getting a statement of intent to issue a death certificate. This means that when she does pass away, you just inform the GP and don't have to call the police out. Speak to the GP about prescribing and leaving end of life medication at the home for when it is required.
The district nurse should be in touch -get a number from them from hospital before she leaves. Give them a ring if they don't contact you within a day or two. Ours were phenomenal and in the final day in particular, came out whenever we needed, no matter the time.
Get some straws in -I know that sounds daft but before she lost consciousness, my Nan couldn't manage to drink from a cup without it spilling so straws were great.
If you can, take shifts with other family members to give everyone some space. Unfortunately, I lacked support and was mostly alone
surviving on about 6 hours of broken sleep in 4 days was not pleasant 
It may help you to read about what to expect in the final stages of life. It really helped me to know what was coming and what to expect.
If you and/or others will be staying at MiLs home in the final weeks/days, make sure there is a stock of tea/coffee/milk and easy to prepare snacks/meals.
If people are staying in their own homes but may be needed during the night, have some warm clothes prepared to chuck on should the need arise. At 2.30am one freezing March night, I was very glad of that!
Finally, make sure you know who to contact if there are issues during the night. My Nana's partner helped her onto the commode one night and then unfortunately, couldn't get her back. He called me out at 2.30am but when I got there (luckily only ten mins away), there was no way I felt confident to move her so called out carers.
Take care of yourself and eachother. It is unbelievably difficult both mentally and physically. I will be eternally grateful that I was with my Nan in her final days and when she died but I don't think I have ever felt so drained in my life.
I hope the time she has left is as peaceful as possible 