Perkiness is the noun: the quality of being perky — that bright, sure, slightly bouncy mood. Informal, a little cute. You might talk about someone’s perkiness at breakfast, or the perkiness of a small dog that has not yet learned the day is long. It can be affectionate, or it can be slightly teasing, as if the cheer is a bit much for the hour. It is not a grand or scientific word. People use it in talk and in light writing, not in serious reports.