Fall is really the best time to move them, assuming your area has adequate rainfall during the winter.
If your plants were pollinated and set seed, they won't go dormant until the seed ripen and are expelled. Some of my Trillium retain their foliage until early fall and I move them then.
I have used two methods to move summer dormant plants: Dig, pot and label them, so I can keep them watered over the summer.
Use a label, stake or other means to identify their location, so that I can find them when I am ready to relocate them.
I had a few locations in my woodlands that were difficult to water, but was solved with the addition of plastic water pipe laid on top of the ground. With the proper fittings, I was able to connect the pipe to one of my outdoor faucets with a hose and have a faucet at the terminal end of the pipe, for a hose connection.
I used ½" irrigation pipe, which is the cheapest and is available in 10' length(some vendors have it in 20' length) and is easy to work with.
A 500' run cost less than $100 and a little time and effort.
Draining the pipe for winter is very easy, I open up both ends and elevate it about 5-6' in the center of the run. Once drained, both ends are closed to prevent trash & insects from entering.
Leaves and pine neddles covered it, so that it's no longer visible.
Wishing you great success!
Rb

Rb, thanks for the good advice. If I may pick your brain once again, my other big roadblock with the space I want to plant is that it was used as a dump of sorts. I'm wondering if instead of digging for anymore surprises I could add some rocks and mix in and mound up some new soil being careful not to smother out the tree trunks. What do you think?