If I were going for an older MacBook I would probably be looking at an early MacBook Air, 1st gen, if it's mainly for music and movies. The one thing that you would need to consider is that it doesn't have an optical drive built in but I picked up an
Amazon Basics External DVD rewriter for less than £30 brand new. I think the Air is good for travelling because of the weight and size but still offers some serious poke under the hood.
I have a White MacBook but there is a serious increase in weight (and heat) and because they are plastic bodied they would be less robust for travelling with.
The MacBook Pro's are more powerful and have built in optical drives but you pay a weight penalty and in addition it doesn't sound like you would need the additional computing power.
You might want to take a look at the refurb store on Apple.com as there are often some real bargains on there and obviously they come with a full warranty.
The Archangel