I totally understand your feelings, but you knew these were non-refundable when you bought them. We might be going down the 19th of December, the last
MVMCP is 20 December. but then, school might not let out til afternoon 20 Dec - 12 hour drive, no way to make the party. I made the decision to not buy tickets. I know Medical is different, but that is the risk we take.
And just imagine how many folks would try to claim medical emergency, how could Disney check it out? So they just have to say no. So, no reason to get mad at Disney, IMHO, sorry.
I sincerely hope your MIL pulls through!