The outdoor event, held at Paltrow's Amagansett, New York, home, honored both Goop's expansion into e-commerce and Net-a-Porter's seasonal same-day delivery to the summer hot spot.
While the actress posed for photos with the likes of Sarah Rutson, vice president of global buying for Net-a-Porter, Molly Sims and pal Jessica Seinfeld, Martin spent time playing around with the couple's children, Apple, 11, and Moses, 9.
The British rocker, 38, asked two of the event's teen valet boys to take his young children for a ride on a golf cart while dinner was served, an attendee revealed to PEOPLE.
The source revealed that a barefoot Martin was very appreciative of the workers, who rode the kids around the neighborhood, and even gifted one of the valets the Love Button pin he was wearing.
Gwyneth Paltrow's Favorite Things
Paltrow, 42, and Martin have been regularly seen spending time together as a family following the finalization of their divorce in April.
The actress has since been dating producer Brad Falchuck. The couple, who've been reportedly dating for over a year, recently returned from a trip to Rome.
Martin has moved on as well, with Oscar-winning actress Jennifer Lawrence. Despite reports of a breakup, the pair were spotted spending the Fourth of July weekend together in New York City.