Kate, 37, looked elegant in a flowing pink L.K.Bennett dress, teamed with her trusty Castaner wedges and a red Mulberry bag, as she kept an eye on her excited little ones.
Meanwhile the Duchess of Sussex dressed down for the outing in a £545 khaki green maxi dress by Lisa Marie Fernandez and a pair of gold aviator sunglasses by favourite designer Stella McCartney.
It is the first time the Sussexes and the Cambridges have been seen together as families since Archie's birth.
It also marks a rare joint appearance for Meghan and Kate, who are typically only seen together at official engagements attended by the entire royal family, such as Trooping the Colour.
Full of energy: Prince George could be seen climbing over supplies in the back of the car - as Louis tucked into some food Princess Charlotte and Prince George appeared to be enjoying their day out at the polo as the children tucked into a picnic tea in the boot of a car Read more from The Daily Mail.