Sorry to read this pink. My dad got a terminal diagnosis in November 2016, initially given 2-3 months. Thanks to chemo he lasted til last January. I am also on Mat leave now, which is a weird mixed blessing, as my impulse is still to go and spend time at the "parents" as his passing is so new I haven't quite processed it.
The year has passed in a flash and at the same time it was incredibly intense and packed full of experiences and moments I'll never forget. It made me prioritise my parents in a way I hadn't done for a while (I am expecting my 3rd baby any day now and the elder two are 1,5 and 3,5 so life has been very busy).
Re: the grief. I found when dad passed that actually a lot of a grieving had happened when we got the devastating diagnosis. I can honestly say I was totally shell-shocked and unable to function for the first few months after his diagnosis. Now I am desperately sad, and I hate that he won't hold and bless our youngest child when he comes. But he was so ill and it was so hard that it was time for him to go.
In the past year we prioritised my parents, I popped over for coffees, lunch, with the kids, without them, we spent weekends with them at the seaside. I visited him in hospital. We celebrated everything we could. We actually had two last Christmases, as he wasn't expected to make it to his final one. We made sure we'd said everything that needed to be said, which mostly was I love you, I've learned so much from you/am so proud of you, I am intensely grateful to be your daughter/dad in the first weeks after the diagnosis. I also told my dad in confidence that we'd really like a third baby, and he knew this little person was well on his way when he passed (which devastated him, to miss the birth).
It is also important I'd say to maintain your health and relationship. Spend time with your husband. Teach him to support you. Have a day off cancer now and again. Look after yourself. You are going through a lot and you are very important too.