When your people are working long hours to get a software engineering job done, you should work the same hours. This sets the right example. Your employees will be more willing to work hard and do a good job if they know you are in the predicament with them. I had a software development manager, Karen Bolda, that did precisely this. It made all the difference in our attitude. During crises, Karen took on the role of "working for her employees." It worked.
If you can't help with the engineering work itself, let them know you are available to coordinate effort, run errands, order food, whatever they need. In short, carry the water.
