I think that your son might have some problems with people mispronuncing his name--but it's important to keep names from one's heritage alive, and that cancels out those potential problems. A patient "It's pronunced [pronunciation]," will usually deter them.
That said, the only name I'd have trouble saying is Predrag. My favourite off of the list is
Dragomir, I think. The meaning is wonderful, the pronunciation is relatively easy to discern, and it looks nice. After that, I like
Andrej a lot, though people might be thrown off by the ending J.
Zoran is the one I'd probably avoid, since it'll sound more like a cheesy sci-fi villain and less like a name with history and familial importance.
I think Serbian names are neat in general, though, and so I'd say that any of those would be a very fine name for your son. Good for you for giving your son a name that reflects his family history!
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