I have problems with terrestrial, too: it means both "of Earth" (see "extraterrestrial") and "like Earth", as in the inner planets.

Do we call the same class of hypothetical planets orbiting other stars "terrestrial"? No, we use "Earthlike".

I'm not happy with the idea of "dwarf planets": it's too easy, and too tempting to name the next seven discovered after Grumpy, Doc, Sleepy, Dopey... On the other hand, naming them Balin, Thorin, Oin, Gloin, Gimli, etc. would lend a touch of class.

I still think "Kuiperian" is a better choice, even if it is my idea: it honors Kuiper in the same way Jupiter's Galilean moons honor Galileo, and it carries with it a reminder of where they orbit.