GerrardWinstanley Re Shopkins - they are collectible figures. Each season has different figures, finishes, limited editions and rare. Each season has: 2 pack, 5 pack, 12 pack and 20 pack tube and then new playsets with limited ed Shopkins in (normally x2). When a new season is released (season 6 - Chef Club has just been released and sounds like what you're DDs have just received) I tend to buy a 20 pack and 2 packs as treat/bribery.
DD only has one playset (Sweet Spot playset - has a working gumball machine) and Shoppie dolls.
Season 5 has been the favourite so far as 5 & 12 packs had a bracelet and the hidden Shopkins were small charms. Also it had glow in the dark Shopkins.
The main issue is storage so I bought a Shopkins display case with Boots points and a mini shopping basket (from a local store).
There is a Shopkins app which 4 and 6 yr old love. There's a slightly more difficult one called Shoppies I think which is like Froggar. Season 6 has a scan bar on it so you scan your Shopkins. I haven't downloaded this one yet as don't have any season 6 yet.