Hi Dave! Welcome to the Camera Labs forum and to te Sony community here! Great to have you join us!
I basically use my 50mm as a walkaround lens, but for many photogs, the 16-80mm Zeiss will be much moch practical. I used to have one, and I've always been satisfied with it, apart from the build, which wasn't nearly as good as the 70-200mm I got as my second lens. I'd still recommend it though, it's great piece of glass. Just make sure you get a 50mm too!
Some people got bothered of us taking snaps of them, and more importantly, their kids, understandably. But yeah, seeing the museum swarmed with Alpha DSLRs was great for change. I only saw two Canons, one Nikon and well over 60 Alphas! Haha!
For indoor purposes, at least the one I frequently encounter, even a constant f/2.8 is not enough at ISO 800. That's what you'd use the 50mm for. Many here on CL even know I shoot at exposures like 1/40 sec, f/1.4 and ISO 3200. A 17-50mm f/2.8 is not gonna get you very far in such conditions...
By the way, with a Zeiss 35mm, do you refer to the Zeiss 135mm or the Sony 35mm G lens? I wanna get both, haha, but the 35mm would be up first. For landscapes, that new Zeiss 24mm f/2 SSM might be even better, and probably cheaper too (I hope).
- Bjorn -