First I am so sorry you have to cancel. I've had to do it once and it was heartbreaking. Just know that Disney will be waiting for you when you are more able to go.
So on to your question, I have actually had to cancel things a few times. I paid with my debit card. It took about 5 days on average to have the money back in my account. When I asked about time frame I was told for credit cards (not your debit card with the Visa logo) that Disney refunds the money within 5-7 days and then your credit company will refund it back to you based on their policies. She said typically the money is put back on your next account statement after the CC company recieves the money back. So that could be around 30 days. I have no experience with how true that is though.