If you're not on a tour but travelling on your own, the only time you would have to dress up for dinner is in a finer restaurant, such as a Michelin starred or similar. If just eating in nice family restaurants, whether with other tourists or locals, you should be fine with the dark jeans and a nice shirt. And you shouldn't need an add'l pair of shoes unless your normal touring shoes are white tennies. Decent looking athletic shoes would be fine. I'm not a foodie and I don't frequent Michelin star restaurants and I have never dressed up for dinner in Europe and most of those people I see dining around me are the same. Clean and neat is more important than dressy.