[I love the loose cardigan and never thought to pair it with a button-up which is something else I love.] Layer a looser flowing cardigan over a classic button up for a casual, polished look. A pop belt adds shape and balances out the look.
Check out these suggestions for sightseeing or other travel-comfort wear: leggings, loose tops, comfortable shoes, shoulder tote bags for your camera and other items. With a little 'mixing and matching' you can eliminate over-packing.