Are you good with a soldering iron? If you are, you may try resoldering the 4 corners of the little buttons inside the key fob, carefully because they're tiny. They do wear with age and may break contact. Happened on one of mine. Might just be coincidence that they both stopped working at the same time. When mine went, however, not all the buttons went at the same time. I had problems with the lock button, but trunk and unlock still worked.
Still, worth checking it out.