Gwen Stefani and Gavin Rossdale took Kingston and Zuma along to spend yesterday at Joel Silver's Memorial Day party in Malibu. Gwen and Gavin were one of many famous couples at Joel's get-together. Tom Cruise and Katie Holmes, as well as Guy Ritchie and his pregnant girlfriend, Jacqui Ainsley, also attended the bash. The Stefani-Rossdale family strolled on the beach together, with the boys playing on the sand in their swim trunks while mom stayed cozy in a leather jacket. It was one of many afternoons the foursome has spent by the water recently. They just returned home from a trip to Cannes, where Gwen wore a bikini on the deck of a yacht and Kingston even tried his hand at jet-skiing. The fun of the last few weeks included Kingston's fifth birthday last Thursday, which Gwen and Gavin celebrated by taking him out for lunch on the big day.