Cuillin, six, and Lejla, four, designed the memorial plaque which was installed in the Commons chamber today as part of a "family day" in Parliament.
MPs and staff have been encouraged to bring their children into the chamber, and there was a special question time where the youngsters quizzed Commons Speaker John Bercow on how Parliament works.
Inspired by Mrs Cox's maiden speech, which contained the line "we are far more united and have far more in common than that which divides us", the plaque bears the motto "More in Common".
It also has elements to show Mrs Cox's love of rivers and mountains and her support for women, as well as four roses to represent each of her family members - two red for Labour and two white for Yorkshire.
The unveiling - which was rescheduled due to the General Election - comes shortly after the first anniversary of the Labour MP's murder by right-wing extremist Thomas Mair as she arrived to host a surgery in her Batley and Spen constituency.
MPs killed while in office are traditionally remembered by heraldic shields in the Commons.
As well as honouring MPs who fell during military campaigns, there are also shields in memory of Conservative MP Ian Gow, who was killed by an IRA car bomb in 1990, and Tory shadow Northern Ireland secretary Airey Neave, who died in a car bomb attack in Westminster in 1979.