The path of violence or peaceful, depends what message you want to tell.
Your enemies are cute, they are smiling, they are rounded, they do not look like they are bad. Example, Goomba from Mario universe, they look cute, but they have eyebrows in "V" and sharp teeth, that turn they some kind of bad guy or make us fill that way. Do you understand? Is the shape of the things that also tell stories. That is why I thought "maybe the developer does not want us to kill them", but you give us points to do that. Put something to turn them into bad guys.
The "Star-Attack" also depends how you want your players play your game. If you want that they have a limited resource to choose wisely when to use or smash the button to kill them all.
Mario when he is on Fire form, only two fireballs may be thrown at once. If you want the resource to be infinite, that is an example. If the stars are finite, maintain showing it in the HUD, if they are infinite, you do not need to show how many stars you have.
See, it is complicated. You can choose a bunch of things. The thing that I recommend is try to make the things consistent.
How your game runs on a cellphone, people play in a short period of time. So make it simple. The average of people who plays in their phones, does not play to think about the meaning of life or what is good or bad. On mobile, put something fun with a short core loop and ads between the game overs hahahahaha.
Just keep practicing and keep it simple.
