Campaign prep for the high fantasy one-shot

Because of the Thanksgiving holiday week a couple of us in the group are anticipating a less than adequate showing for keeping any kind of story continuity for our main campaign. Thus, another one shot. I volunteered to run it, and we settled on a higher level game for this, just to it out. Our other option was a grittier roll 3d6 take the stats in order lower level campaign. Both are appealing. We will likely do the other one in the future, just for kicks.

As soon as I accepted responsability for this I had some kind of idea for what I wanted to do. I really like the larger than life fantasy craziness. I liked Eberron. I wanted to run something in a world with cool stuff. The elevator pitch for it would be something like:

High magic meets Waterworld, an island dominant world with no limitations on what magic can do. The adventurers must board a flying, living castle, and discover what, if any, threat it's occupants pose to their homeland.

Short because this is just a one shot? Anyhow, the idea is that similar to Christopher Perkins' Dragon Sea setting, this world is mostly water, with islands of civilization dotting the globe. Our players are from one such island, confidants, retainers, servants, or mercenaries of the King. This world also has several Castles, flying citadels inhabited by powerful mages. The Castles are living cities, filled with Arcane schools and study. Here is part of what I sent to the players:

A Castle was drifting south, towards the island. There were no
skyships docked in it's moorings. No lanterns hung from the towers.
He did not dare get closer to investigate. But if a Castle was headed
for Actevona, it did not matter it's condition. By Bram's estimates
the King had less than two days to do something about the Castle
before it was within siege distance of the kingdom.

This will be our highest game so far, at 11th level. I was pretty excited to try my hand at running some different creatures. I have four encounters put together with maps, tactics, visuals, and whatnot. I am debating how much, if any treasure to put in the game. It is only a one shot, but being rewarded is nice.

We will see in about a week's time how this worked out.

Jay