Oh wow. We are in the same shoes as you with Delta. We cancelled our flights while at the airport in Detroit back on March 13th. We also were told it would just be a credit good for 2 years. We have not received any refund. Maybe I will give them a call this weekend and see if anything has changed. Lord what a crazy day that was looking back with so many family members and friends calling and texting us to get back to Canada ASAP because Trudeau was closing the boarder in like an hour and we would not be allowed back into Canada. Never mind that the day before Doug Ford was saying on the radio to go ahead and enjoy your March Break and travel, everything was just fine. Good times!!
Oh boy! My neighbors were in a similar spot as you, they had just left Detroit and arrived in Orlando only to have friends and family tell them to get back home asap. They were very skeptical about going but everyone said it was fine to go, how fast things change. I plan on contacting Delta too, I am totally mystified over why the kids' tickets were refunded (nothing on our tickets yet).