Khloe, Kourtney and Kris Go Shopping for Baby

09/23/2009 at 05:55 PM EDT

Khloe Kardashian took a break from wedding preparations to join her pregnant sister Kourtney for a baby shopping spree in Beverly Hills.

With a camera crew from their E! show Keeping Up With the Kardashians in tow, the women visited several stores Tuesday, and mom Kris joined her daughters for part of the shopping trip.

During a stop at Kitson Kids, "Khloe happily posed with a kids-size L.A. Lakers lamp," says an onlooker. They also visited Auntie Barbara's Kids and according to an eyewitness, "Kourtney kept the sex of her baby secret by looking at both blue and pink baby clothes."

While Khloe again kept mum about her upcoming nuptials, mom Kris pretended to be surprised when a photographer asked her about the wedding. "Khloe and Lamar are getting married? Shocking!" she joked.

Later Tuesday night, Khloe and fiancé Lamar Odom of the Los Angeles Lakers – who are getting married Sunday – stopped by the NSF and GQ Magazine's Stop Puppy Mills/Humane Society of the U.S. Benefit at a private estate in Los Angeles. Neither would comment on the wedding. When asked about Sunday, Odom replied, "What's on Sunday?"