I'm so sorry, OP. Wishing you strength and support right now. I hope you will come back here for support as needed.
I have not lost a child, but I have lost both of my parents and a brother in the past few years, and I can say that you will probably be kept very busy in the days and immediate couple of weeks after her passing. I would suggest considering some kind of funeral ritual for a couple of reasons -- one, because your parents and other loved ones will be here and will want want to be supportive and be part of a ritual to honor her life and death, and two, because it will give you something to do to channel the grief and energy and to occupy the time immediately after her death. I have come to believe that funeral rituals are useful not only in a ceremonial way, but maybe primarily because they keep you functioning at some practical level in the days immediately after the shock of loss.
Maybe think about some way that the people who love you and her can come together to support one another...even something as simple as a luncheon where your friends, family, and her caregivers could gather to support each other and say goodbye to her. I know you say that scattering her ashes is not something you are ready for yet, but there are other rituals you could build around her death that might be supportive and meaningful.
As for her stuff, if you can spare her room for a while (depending on the timing of your pregnancy and what your space needs are) I would highly recommend that you hold off on making any decisions about her things yet. You are kind and understanding to take your DH's feelings into account. And you may feel differently about what you want to save and what is too painful even a month or two months from now. So if you can just close the door, I suggest doing so.