Your lens choices exactly match up with mine. I have and use the 28/1.8 on the 1.3x body with good results. The soft corners only show up with shooting wide open and usually it is never an issue.
I see you have the 24-70/2.8L listed. (I also understand you do not want to take the L zooms with you on this trip). For my needs when traveling "light" with a 1D or 1D mkII my 28-70/2.8 and the 50/1.4 makes a very good combination. The 28-70 takes up about the same space and weight as my 28/50/85 and gives up little in image qualtiy with less lens switching The 50/1.4 is my evening/street lens.
If your a wide angle lover or PJ style shooter the suggestions to take a 17-40/16-35 may be a better way to go. I am not trying to talk you out of going with your primes just suggesting you examine why you want to shift to primes for this trip when you have some great lenses in your kit already.