Hi ndorfin - whilst we love that young kids are playing the game, they aren't our primary audience. We're making a game we want to play - and that necessitates a modicum of challenge in campaign mode, even on the easiest difficulty setting.
However, we will in the next few weeks be releasing Freeplay mode, which is probably much more suited to very young players. It doesn't have objectives you have to complete, or time limits, or anything like that. You simply grow your colony over time. You'll be able to set up the initial conditions to make the game endless, and it'll feel much more like a "pet colony" if you want it to.