If you have the model for the castle we could recreate the whole scene (without the fireworks though).
It's a bit dark, so I couldn't see all the details, but a simple powerfractal terrain (not too much displacement and not to large features), with a painted and displaced river and a water plane, and a simple population should do the trick. Tune down the sun strength, add some standard low 3d cumulus clouds, and pull back the camera over 150 frames.
Setting that up might take half an hour (perhaps 2 hours with heavy tweaking the details), and rendering time would depend on the system and resolution. I'd say a week for the entire animation on a regular home system at 720 x 480.
