Shi 'n Pax, out on the town!

On Saturday, Shiloh Jolie-Pitt, 3, and her big brother Pax, 6, left the confines of the Venice palazzo they share with parents Brad Pitt, Angelina Jolie and four siblings.

Escorted by grandparents William and Jane Pitt (Brad's parents), the buddies enjoyed the spring sunshine as they hit the Italian city's famed Piazzo San Marco. Grandma and Grandpa Pitt have been staying with the brood at the $6.8 million palace since early last week.

Shiloh and Pax's mission that day: gelato, naturally!

The Jolie-Pitt kids have been enjoying local ice cream -- in cups and in cones -- ever since touching down in Venice in February as mom Angelina, 34, prepped to film The Tourist.

"Those kids will turn into gelato soon!" a source jokes to Us.