Depends on who you eat & pray with - according to a book on etiquette for Catholic priests I read long ago, grace is to be said in a language everybody/most people present can understand.
The Latin blessing you refer to (Benedic, Domine, nos et haec tua dona, quae de tua largitate sumus sumpturi) is also traditionally reserved for the priest/abbot (at least, so I've seen it done by the Benedictines). I suppose if you eat alone/with no priest present, it's no scandal to use either formula, since you don't intend to usurp any priestly privileges. Moreover, Greek prayer books for laypeople include it, with no mention that it's reserved for priests.
Certain prayers are traditionally reserved for the "Eldest" (gerontika): Psalm 103/104 from Vespers or "Vouchsafe, O Lord, to keep us this night", but if he/she's not present or one prays alone, the next in rank/you yourself can read them.