I usually start these from seed in a community pot and when they are about this size is when I sometimes pot them out into individual pots. I've always bare rooted them when transplanting at this age.
That said, I grow them in coconut coir seedling mix that washes off the roots really easy. There's very little/no root damage from my typical transplants at this age.
Your situation is much different. If they are in damp soil along a pond, the soil is probably quite a bit heavier than what I sprout these guys in. Even shoveling out a ball of heavy soil may be moving the soil enough to break tiny roots
You may also be fighting the issue that "in the wild" the damp soil by the pond has a wider ecosystem to balance fungal issues, bacteria, etc...when moving them to pots, the balance may be tipping in favor of the bad guys
I think what I would do is get some sterile seedling mix. Coconut coir, perlite, or a mix of both. Bring a spray bottle and a butter knife and try to gently lift one seedling at a time. Once to do one or two, you should get a feel for how wide the roots may be, but try to take as little soil and break as few roots as you can. This is where the spray bottle helps. You can use the butter knife to scrape away soil and dig down much more gently than a shovel. Use the spray bottle to help wash away the soil you've loosened up. If you can lift one without breaking too many tiny roots, you should be able to easily plant them into a light seedling mix. Spray the roots with the spray bottle to keep them moist as needed.
I don't care for all the litter I see in your six pack of seedlings
That might work well in the wild, but bring it into tiny pots and there are too many variables to control. Get them in a light, sterile mix and you should have better success with tiny pots.
All that said, if you miss your opportunity this year and run out of seedlings to collect, collect a few cones in the fall. They're easy to break apart and harvest the seed out of. They germinate readily with the right pre-treatment which is basically just toss them in a baggie of damp sphagnum and throw them in the bottom of your refrigerator for a few months. That's where all mine have come from. My office campus has a number of trees and I would grab cones when out walking during lunch
Good luck! I hope you can successfully grab yourself a few this season yet!