KETTERING, OH— Jeffrey Dumas, a developmentally disabled 12-year-old, receives a new PlayStation 2 video game right before every dinner party thrown by his parents. "Look, Jeffrey, a driving game!" said Meredith Dumas, 40, presenting her son with "Gran Turismo 3" and a box of snack crackers minutes before guests began arriving for a party Sunday. "I bet you could get a million points by bedtime if you started now!" The haul was one of Dumas' best since New Year's Eve, when a party thrown by his parents netted him "WWF Smackdown!," "Crash Bandicoot 2: Cortex Strikes Back," and "Simpsons: Road Rage."