If you thought Valentine's Day was the Super Bowl of dining out think again. Mother's Day claims the prize for getting the most diners in the door, in any booth they can find. "The second we open the doors, it's go," said Tim Davin, director of operations for NCR (Next Cool Restaurants) Ventures, a group of neighborhood restaurants with nine locations and six brands. Davin said Mother's Day outpaces every other major dining holiday on the cale…