technically, the diminutive τεκνίον would be more appropriate in this context. Teknon was more formal, and in its colloquial usage was used commonly in the stereotyped phrase "women and children", which in the ancient world was a symbol of low social status. The diminuative would indicate a different usage, more affectionate, friendly, etc.
What, was he speaking Greek?
Roman elites spoke a lot of Greek among themselves, a bit similar to how Tsarist nobility used French
Sure, I mean obviously he knew Greek, but I'd never heard anyone assert that his last words were in Greek!