+1. I think there are few choices that (i) can be dressed down or up (I´ve seen these paired with sportcoats in Europe), (ii) are comfortable, (iii) are reasonably durable, (iv) are readily available, (v) fit in with your age, and (vi) won´t cost you big bucks.
Even so, these are more comfortable with good third-party inserts such as PowerStep).
Also, since you are walking a lot you might want to ditch the sf approved sneaker and get a pair of brooks that fit your running/walking style. They will be easier on your feet and are made of mesh so your feet will breath better.
DO NOT TAKE ONLY ONE PAIR OF SHOES. You can stuff your socks in the pair you pack.
Of the top of my head I would pick a pair of dark tan Sebago Schooners and a pair of black Stan Smiths. But if it were me it would be Chestnut RM William Dynamic Flex boots and a pair of Hanwag Puros.