Right after Christmas I will visit the country of my birth and I am determined to take the best portraits of my mother, siblings, etc. as I can (not in a studio, just outdoors). I have the knowledge and skill to do that but not the proper gear. I am limited to my 24-105 f4L ( I can't really melt the background the way I want it) and the 50 1.8 II (the pentagonal bokeh balls drive me nuts). I returned the 85mm 1.8 in my signature below to help pay for my car insurance deductible (life happens).
What you didn't really touch on is what your constraints are in terms of luggage. When travelling by air, I usually find we reach for the 70-200 f/4 L IS, rather than the f/2.8 IS II - purely for weight reasons.
If your requirements while travelling are mainly for portraiture, and weight is an issue, you could consider a 50 mm f/1.4 and an 85 mm f/1.8.
A 70-200 is still, overall, a more versatile lens, and if you can handle the weight in your luggage, go for it.