I REALLY like this game. I think it's a really well put together Tower Defense title. I have a couple suggestions. One would be to add the ability to choose which enemies a tower will target (First, Last, Strongest, Weakest). Also, it might be a bit OP, but upgrading to have a second, weaker Demon child. A big one for me, is the star rating. I realize it demotes you as soon as your first non-demon child gets captured, even if for only a second. You could allow a player to regain the third star if only a single non-demon child has been captured and returned, and then never captured again. You could set the game so that if that first non-demon child gets captured for less than say 5 seconds, when that child returns back to base, you'd regain the star you lost. If it were to happen again, the star would be lost for that attempt.
Keep up the good work!