I am a manufacturer/retailer, so I totally understand delays this time of year. But, just communicate! And, make the communication personal. That is all you have to do, and customers are willing to be patient about 98% of the time in my experience.
I advocate four steps:
1-Proactively write customers who are facing an added delay of more than a few days.
2-Apologize and explain what is causing the delay. Be honest and specific about their order.
3-Tell the customer when they can expect to see that their package has shipped - even if it is a week from now. Much better to give real info than reassuring with generalizations.
4-Nicely thank them for their patience, but don’t use fake effusiveness.
You guys make great products, you just need a little pro-active communication, and when you respond to communication from customers, make your responses personal. They extra time and manpower required to to it will pay off 10x in customer appreciation and loyalty.