Beth Ostrosky finished Sunday in 4 hours, 15 minutes - much better than the five-hour target the 36-year-old former model was aiming for.
"This was the happiest day of my life," said Ostrosky, who ran to raise money for Long Island's North Shore Animal League.
"Isn't she beautiful?" Stern gushed as daughter Ashley, 15, also hugged her stepmom.
Stern, 54, who married Ostrosky last month, had done his part that morning: Making a carb-loaded breakfast of bagels stuffed with peanut butter and bananas.
"She ate a ton," he said.
More food was on the way after the race. "We're going to celebrate with some sushi and some pasta," Ostrosky said. "A lot of sushi and pasta."
Ostrosky said what kept her going most through the more than 26-mile course was, "I just kept thinking about seeing Howard and Ashley on the finish line."