Cannot this be translated to: "where are the boys running?" ? Is it necessary to say "running to"?
I would say ' Where are the boys running' in English. The 'to' sounds unnatural.
So when I use לאן, I'm asking where to? What should I use to ask for the location, איפו?
That's right. איפה.
You can add ל to make it לאיפה, which is where to.
where are they running, does not imply location. Location would be where do they run?
"Where are they running to?" is grammatically incorrect in English, since the preposition is at the end of the sentence. Still, there are many sentences that no one criticizes for having a preposition at the end because it's common usage. In this case, this sentence sounds like most people WOULD leave off the final "to," although it is a better translation.