I bought Hero Kids and a bundle of adventures and played Basement O' Rats and Escape from the Ghost Pirates with my kids (now 7 and 5).
The game itself is pretty good. It's simple enough and nicely enough presented to appeal to kids, and cutting out and gluing the miniatures to use on the playing mat was a fun exercise for them (which they mostly did when they were 5 and 3). The adventure maps look good.
The problem is, the two adventures I played are dead boring. They are in the form: description, fight, description, fight, ... There's very little enemy variety within the adventure and very little in the way of interaction with characters. I had to make quite a few changes to make it more fun, and even then it wasn't that great. It's also hard to expand the adventures or create my own because there are few figures for extra enemies beyond those in the adventures.
The reason I came here to review this was having just bought The Cloud Dungeon. As an adventure the Cloud Dungeon is much more inventive, includes several player choices and varied enemies, and there's the part of physically modifying the character image, which should add to the fun. All in all, it looks to me like a more interesting and engaging experience for kids.
On the other hand, The Cloud Dungeon is just one adventure, and Hero Kids feels like more of an RPG framework. If it offered the tools to become a real RPG, such as a monster compendium, then a parent could easily create campaigns and not be limited to what's available. Without this I feel that the game is incomplete, and requires a lot of massaging, at which point it's not that much more attractive than taking another game (D&D, Pathfinder, whatever), simplifying it, and using the large amount of materials available for that game instead of the limited amount available for Hero Kids.