Gwyneth Paltrow threw a star-studded bash for her son Moses' seventh birthday on Saturday (06.04.13).The 40-year-old actress - who released her new healthy cook book 'It's All Good' and launched her fourth fitness studio with exercise expert Tracy Anderson in Los Angeles this week - and her Coldplay star husband Chris Martin were joined by guests including Kate Hudson, Tobey Maguire, Cameron Diaz, Gwen Stefani and Joel Madden, as well as all their children, at their new mansion in Brentwood, California to celebrate ahead of their son's seventh birthday tomorrow (08.04.13).A source told E! News: "Chris Martin was walking around the party barefoot, totally relaxed and having a good time. He spent a lot of time sitting with Maria Shriver and her kids chatting."Kate Hudson talked to Jon Favreau for awhile. Everyone was dressed casually in summer clothes and sunglasses. It looked like a relaxed atmosphere where they could show off their new house and celebrate their son's birthday. People stayed all day and really enjoyed themselves."The celebrity children spent the day playing with hula-hoops, tabletop football, basketball and dancing on the lawn in the middle of the property.The 'Iron Man 3' star also put aside her strict gluten-free, low-carb diet and treated the guests to hamburgers, fries and several different types of salad.Noticeably absent from the bash were the couple's best pals Beyonce, Jay-Z and their daughter Blue Ivy Carter, who are currently celebrating their fifth wedding anniversary in Cuba.'Good Charlotte' rocker Joel brought his two children Harlow and Sparrow but his wife Nicole Richie did not attend as she is on holiday in St Barts with friends including Jessica Alba.