Zoia, I'm unfamiliar with that geranium; it's very pretty. I'm not planning on a "full-on cottage garden"; I know what that's like (been there, done that). The new bed is going to be mostly daylilies and enough perennials mixed in to provide other colors, heights, backdrop, etc. I have no doubt it will be work to keep it from becoming too crowded; at the moment there is a lot of space though I'm sure it will fill up quickly.
My "old" daylily bed is going to become irises, and other fairly deer-resistant perennials - no more "deer salad". There are some daylilies which will stay in that area, though most of them are moving to the new bed.