The hungry boys headed toward the dining hall.

Literal

Belly [possessive-の] empty boys [topic-は], cafeteria [possessive-の] direction [direction-へ] advanced.

腹の減った男の子たち is a relative clause: 'boys whose bellies were empty.' 食堂の方へ means 'toward the dining hall' — 方 (ほう) indicates direction/side.