How do I approve my childs purchase if I don't have an apple device myself?

I added my child to my family account from when I used an iPhone. I currently use Android. I turned on ask to buy through an old mac book. Moving forward, will I have to dig out my old mac book when my child wants to download an app or is there a way to do this through the web? Also, is there an option to make "ask to buy" for paid apps only?