they most certainly will refund the money to you.
of course since you are more than 48 hours in advance, they will refund it. but they also will make exceptions. when we went in may, we came with my brother and his girlfriend. we were doing the luau, and had prepaid our reservations
the morning of the day we were to go to the luau, my brother became very sick. I called disney dining and explained how we were not able to go to the luau, and how much we were going to miss seeing it.
they were very understanding and were able to refund to us the money we had spent.
give disney dining a call and explain it to them. they'll refund it to you.
sorry to hear about your mom though.
jen