Non-Disney fireworks are generally much easier because you don't have a static object in the picture (like a castle) so camera shake isn't as noticable.
The picture is OK but you can see that the castle is a little blurry and "soft" - 1/6th is awfully long to handhold, so you'd need some kind of support. Since you're using a PnS, a small pocket tripod could make a world of difference, as could a Gorillapod. There are many places where you can set up such things.
The steadying influence of a tripod, plus a slightly longer shutter time, would brighten and sharpen up the castle dramatically, and I think you'd be really pleased with the results.