It depends on what type of photography that you intend to do for "walk around travel". I take it you want something light not a heavy back pack but something easy and can do all focal lengths.
A few weeks ago we spent time with my daughter in Havre de grace, MD. I took my basic "wedding" back pack so it has all lenses and two bodies (28/3.5,50/1.8,85/1.8,55-200kit. Well what did I use 50/1.8 at the Baltimore Aquarium and the 55-200 at the parks in Havre de grace.
What I learned and what will be my next purchase for traveling light(?). I would look to an 18-200mm lens either used or new it will not be fast but you are walking around during the day light and with D7K boost the ISO as long as its exposed well you'll be fine. This lens will be wide and give you a good zoom. Again you are not selling images or doing something for a client. Remember earlier I said my "wedding" back pack. So my 2¢ is 35/1.8 that will be great for low light and the 18-200mm (Nikon, Sigma and Tamrom) would be my choice with gear you have.
I would look at KEH for a used (6 mon warranty and generous return policy) or even Cameta for refurbished and then B&H and Adorama but thats my order of preference.
So if you think about it the D7K and two lenses the one you have and the one I mentioned would be a breeze. Oh BTW I use two systems the second system has a 2.8 55-200 and its heavy.
I know you will get all kind of answers.
Ciao,
Lou Cioccio