Hi C.,
My goodness, you have so much on your plate! My heart goes out to you as traverse through your mother's final days. I'm glad your husband is there for you, but do you have other support? Sounds like you're taking care of a lot of people......hope there's time in there to attend to your own needs.
My children both had sensory integration probs. My daughter in particular had an anxiety disorder (Selective Mutism), and her sensory issues went hand-in-hand. She was in OT 3x week for 6-9 months when she was a toddler, and I spent a lot of time doing the "sensory diet" (not food, but other activities) at home.
Someone mentioned "The Out of Sync Child". Unless something new has come along, it is "The Bible" of Sensory Integration Disorder. You be reminded of your daughter on many pages, and you may find things there to try that will help. If you look at http://www.out-of-sync-child.com you will see her new book as well, that offers many activities.
I do hope that at some point, you can find an OT who specializes in Sensory Integration. It would be great if you had someone other than yourself working with your daughter. OT is like play.....the kids love it. I'm not so familiar with how it looks for older children, but my guess is, the activities feel so good, that she will love it. And you certainly may find that with time and knowledge about ways to cope, her hyperactivity may lessen.
Having said all that, you have so much going on right now, I personally wouldn't worry that you have to do something immediately. I can tell from your words that you care very much about your children. I hope you can take some comfort in knowing that your daughter will be okay even if you are human and have limited amounts of time and energy. I'm having trouble expressing what I mean, but maybe you get my gist?
Peace be with you and yours......I'm sure everyone here will be thinking of/praying for you.
P.S. Here is a website of groups in Charlotte that may offer grief support to your family. http://www.supportworks.org/cat709.htm