Rachel, I've loved reading about your yard and garden hopes. I share your issues with vinca and English ivy, though. In my case, I'm the one to blame, for a decade or so ago I thought it would be attractive to have those plants in my rock garden. What a mistake that was! I'm now overrun with them. And since so many of my plants are among the rocks, it's not easy to get down on hands and knees to confront them. I've decided to try sitting on an old milk crate, and slowly making my way around the garden. Might that work for you? I think we both have our work cut out for a long time, though. LOL!
To hold the banks of your stream, might you be able to make use of some more of the rocks that you have?
I've looked at your photo showing the plants to the right of the large trees. If it's an ID of the cluster of narrow upright leaves that you want, they look like daylilies to me. Perhaps they are the native New England orange variety. There's another small broad-leaved plant just to the right of the tree. That looks like a baby maple tree. Also to the right is a magenta-flowering plant that looks like a Lunaria (also called money plant or silver dollar plant). Those are biennial. They bloom in the second year and set nice seed pods that resemble silver coins when their outer covering is peeled off. They will often self sow, so you might gain more of those.
You've got a long-term project with the ivy and vinca, so try not to get disappointed if you don't get it done as quickly as you'd like. Enjoy your lovely yard this summer.
Kat
