This was originally a comment that got too big. Since I wont address the real heart of your question, it is CW. I hope this is ok :/

I am also teaching Multivar out of Stewart this semester. As it has been suggested, I stick fairly close to the book, even working through some of the same examples he does. I focus very hard on motivating the ideas from the ground up.

For instance when talking about curvature, I made the students try to define curvature for themselves. Then proceeded to find little issues with their definitions, until we arrived at something that was pretty close to the standard defn(with lots of urging).

Just yesterday Terry Tao posted a link to this video;

http://www.youtube.com/watch?v=BlvKWEvKSi8

which talks about this exact style of teaching. I think that it works very well for Calc 3, where many of the students are pretty decent at math to get to that point. In so far as specific examples and motivation, I really enjoy the notes by Oliver Knill;

http://abel.math.harvard.edu/~knill//teaching/math21a/index.html

There are some nice diagrams, examples, and explanations of pretty much everything in Calc 3. In particular, he gives real physical applications of the ideas, and at the end he gives a "calc beyond calc" intro.