All 4 of my kids are into scratch but are sort of hitting a wall doing it online, and they also have expressed interest in robotics, so I did research on the two and came up with the mBot series of robots.

For the 11 and 9 year old: the mBot Ultimate (https://www.makeblock.com/pages/mbot-ultimate-robotics-kit)

For the 7 and 5 year old: I wasnt sure whether to go with the mBot Ranger or the mBot2 Rover and went with the Rover (https://www.makeblock.com/products/buy-mbot2-rover-emo-robot)