Congratulations on your ducklings!
First of all, I coddle my ducks. I literally have ducks instead of human children.
Do your ducklings have heat outdoors in their coop? If so they are fine outside, but they still need a "brooder" type environment to live in at 8 and 16 days old. I don't know how cold it gets where you are but most people follow the guidelines of 90 degrees for the first week, and reduce the temperature by 5 degrees each week until they are fully feathered or you reach the temperature of the environment. And also provide a cooler area they can choose to go to if they get too warm.
My ducks are 6 and 7 years old and live in a barn. I have a camera in the barn that I can watch live inside my house and during thunderstorms or hail they are visibly upset. They quack loudly for me. I go in there and sit with them until it passes. They stop quacking and running around, sit down next to me, and relax. But since yours aren't bonded to you I think you should probably just leave them. Until you are a source of safety you will probably just be one more scary thing.
You can be a source of safety! I adopted 3 ducks as adults and they were terrified of me. When they saw me they ran in the other direction and hid in corners. Within months I had tamed them to eat from my hands, enjoy sitting next to me, run to me when they saw a scary hawk, come when I called, and one even hopped into my lap regularly.
I avoided doing anything scary. I avoided direct eye contact. I avoided startling them, moving quickly, walking directly at them, ect. My ducks didn't like it when I stood up tall next to them, so I crawled a few feet away before standing. So pay attention to what scares your babies and don't do it. (I don't have to do any of this stuff anymore, btw)
I made sure everytime my ducks saw me something positive happened. My ducks loved mealworms and tomatoes. So I threw them their favorite treat anytime I walked past their aviary.
And I spent lots of time hanging out with them being still. I knitting near them, read books, even ate dinner and took naps. The more time you hang out with them the better.
My ducks aren't imprinted on me, and I think your ducks are too old to be as well. But they can be friendly and trust you.