That article - just like all other sources - mentions one 8-year-old girl, not "many innocents" and not several children either. Hence, this is deliberate misinformation.
> You can't determine where the device is when the bomb is activated.
You absolutely can. It's highly likely to be in the targeted person's pocket. Where else would it be?
After all, people usually don't hand their phones to random strangers or leave them lying around - and those pagers aren't even mere personal devices used for private purposes. Why would any of those devices end up anywhere else but the pocket of the person using it?
> This is an indiscriminate attack.
Launching rockets at civilians is. Blowing up pagers explicitly used for terrorist activities isn't.