Along with checking/replacing the battery, if the car will still not function with the FOB then you can pull the key out from the FOB to lock/unlock the doors manually for access. You can then insert the FOB directly into the slot as shown via the picture below:
At that point the vehicle should be able to function until you can get the main issue resolved.
To remove the key, on the back of the FOB is a sliding button....slide it down and pull the keychain to extract the key. Here's a FOB with the key removed:
Sorry to hear about your loss.