First, they may be in shock - that will prevent their digestive system from working correctly.
So, I would not delay for more than another 12 to 16 hours, but I would take a step back, give them time in a tub of lukewarm water, and just chat with them a little bit. That may help everyone's nerves, including your own.
When Sechs needed anti inflammatory and antibiotic, I got it in liquid form, and mashed it into peas. She was not thrilled the first day, but by the next day she was doing better (she was eggbound), and so it worked well.
Turmeric is an herb that stains skin and clothes, but it is a natural anti inflammatory, and that may help the ducks a little. You could try putting some in their water. Are they drinking? If so, turmeric might help. Or for tonight and tomorrow morning, a teaspoon of apple cider vinegar per quart of drinking water may provide some electrolytes and help them get through the initial shock.
There is a video on syringe-feeding a goose that might help you, but I would not recommend you bothering with that tonight.
hugs.