35mm is such a cool focal length. I own the 35L as well as the 50L and 50 1.4. The 50L has a nicer bokeh than the 1.4 and feels better. Its a bit sharper below f2.8 than the 1.4 lens but after that the 1.4 is better. I have a love hate with the 16-35mm II. It has some serious distortion between 16-24mm, mine looks soft in the corners below f/4 as well. But that 16mm can produce some cool landscapes. If you want lowlight though, I'd go 24mm 1.4
+1. Love the 35L on a crop body and love the 50L on a FF. My 35L does better with closer subjects because it has a shorter MFD.
It seems to me that you are actually asking two questions:
1. Which is a better wide angle option: 16-35L or 24L? I'd suggest the 16-35L to complement your 28-300L better for your trip. The 24L is a great lens, but there are so many options at 24mm (wide angle zoom, mid range zoom, prime, tilt shift, etc) that the focal length is easy to cover.
2. Which is a better portrait lens: 50L or 85L? If your 50 f/1.4 works well for you wide open, keep the 50 f/1.4 and add the 85L. It'll give you more flexibility. If the reason you're considering selling your 50 f/1.4 is because it doesn't perform as well as you'd like wide open, then it'd make sense to replace it with the 50L if it is your preferred portrait focal length.
If you are able to afford only 1 lens at this time, I'd opt for the 16-35L assuming that you're satisfied with the 50 f/1.4 If you're not satisfied with the 50 f/1.4, then I'd get the 50L or 85L first.