I would choose a premium food also, especially for the boys to minimize their chances of blocking.

But more importantly, on the balcony thing - only when supervised! I would also put leashes on them also, but they still have to be supervised with leashes on so they don't jump off and end up strangling themselves! One way to cat proof the sides is to get some chicken wire or similar type material and attach it to the railings. I know they make plastic material that is similar, but you'd probably want to find something that "disappears" when you look at it. However, if with the sides cat proofed, they will still try to jump up on the railings and that's where the supervision comes in. I don't really know, but to me it seems that 10' is nothing for a cat, especially a curious cat!