OP here, and thanks everyone. Yes, I am hosting, but I think keeping myself busy today and surrounded by family tomorrow (including my brother and his family) is the better call for us. It's potluck, so I don't have to make much myself, and I'll probably slack off a bit on the housecleaning, but cancelling altogether or even ordering pizza will probably just make everyone more sad.
I had a good cry, DH came home and gave me a good hug, and I picked myself up and headed to the store. Just have to try not to cry at all the happy people today. Prayers for my brother. Thanks all.