Traveling to Belgrade - First Time & Need Recommendations

My son and I are traveling to Belgrade in June. We'll stay in Belgrade at least 5 days, at which point we'll rent a car and drive to Novi Sad. I'm half Croatian and Montengrin, but we wanted to check out Serbia.

My son and I share similar tastes. We like to shop (really enjoy outdoor markets), eat and explore walkable and interesting streets. We like the occasional museum and historic site, but try to avoud the tourist traps. We do not care about brutalist architecture, but we do like old-school Yugoslavian vibes. Particularly music wise, with bands like Bjelo Dugme, Crvena Jabuka and Divlje Jagode.

My son has never been to this part of Europe and he's 10, but very mature for his age. So far, we're thinking about visiting the following:

1. Knez Mihailova Street
2. Skadarlija
3. Kralja Petra Street (is this Dorcol?)
4. Kej Oslobodenja (is this the Belgrade Waterfront with the new mall?)
5. Bulevar Kralja

We also want to check out the Historical Museum of Serbia and Hotel Moscow. Happy to take any recommendations, particularly with respect to food: Burek, Cevapi, Pljeskavica and whatever else you would recommend.