For Tony:
* Αντώνης (Antonis): This is the most common and closest equivalent. It's a classic Greek name, and while not phonetically identical, it's a familiar and readily understood name.
For Tonia:
* Αντωνία (Antonia): This is the feminine equivalent of Antonis and the closest translation. Again, a classic and widely understood name.
* Τόνια (Tonia): This is a direct transliteration, keeping the original spelling. While understood, it might sound slightly foreign to some.
Therefore, the best choices are likely Αντώνης (Antonis) for Tony and Αντωνία (Antonia) for Tonia. They are both natural-sounding Greek names.