I don´t know of any vegan coffeeshop in amsterdam. I´m sure though, that at kokopelli (warmoesstraat 12) you´ll be able to find something for on the train. It´s a nice place. I sometimes just go there for a cup of tea.
I would also recommend trying some indonesian or surinamese food, because it´s probably the first time you would eat indonesian or surinamese stuff and it´s realy different than chinese, indian or thai food. 'Blauw' (amstelveenseweg 158) is a restaurant that has great indonesian food, but there are many good indonesian restaurants in amsterdam.
The best restaurant in amsterdam by far, is 'le ciel blue' on the highest floor of the okura, (you can see it from practically anywhere) but that place is realy VERY expensive. Way beyond a backpackers budget. Both the food and the view are absolutely unrivaled though.
If you have some time left, you could go floating at koan-float (herengracht 321) for half an hour or an hour.