It actually could be his food. My boss had a similar problem with her senior dacshund. He could hold it though the night, because of his feeding schedule, but during the day, he couldn't. He would even deficate in his small crate. They vet said it was partly due to stress but mostly due to his age. I would definately try a different food and see if in time, that helps. I don't know enough about crate training to offer any advice on that, but I would think it would be very hard on him at his age. But I could be wrong. The main thing may be to watch his feeding schedule. Feed him and see how long it takes him to go. Keep a record of it for several days. This is what my boss did, and with the new food and the adjusted feedings, Chance is doing great now.
Hope this helps and good luck.