We stuffed ourselves with pizza and chicken for lunch.
Literal
We [topic-は] lunch [for-に] pizza [and-と] chicken [object-を] to-one's-heart's-content ate.
たらふく is a colloquial/casual adverb meaning 'eating/drinking one's fill, to the point of excess.' Has a slightly playful, gluttonous nuance. 昼飯 is the casual/male word for lunch — 昼食 is the formal version. に marks 昼飯 as the occasion/target ('for lunch').