You'll need SimPE to edit the lots.

This tutorial will help you to navigate to the lot in SimPE:
http://www.modthesims.info/showpost...541&postcount=2

The tutorial was originally written for copying lots in Castaway Stories. You can ignore that part, and follow the tutorial with an intention to edit instead of copy lots.

Back up the directory stated under step 1 (or the appropriate profile if you're not playing as "Default Player"). Follow the tutorial up until step 4. Select the lot. In the lot description editor (step 4), use the Lot Type drop list to switch between residential and community lots. Then commit changes to the lot description, and save the neighborhood package. (No need to follow steps 5 and 6.)

I'm not sure if the map will update accordingly (and remove the Shady Lagoon from the list of available lots to visit), but if it doesn't remove the lot, do not attempt to visit a residential lot by sims who are not residents of that lot. Probably makes the game go boom.

You'll find lots of objects immovable and/or unable to be sold/deleted. While the mechanism of locking objects was useful and logical during the story part (it would be stupid to allow a user to sell the castaways' tents once they infiltrated the Shady Lagoon), EA of course forgot to unlock all objects once the story was over. Luckily, there's a way to get rid of those objects.

You can try using Pescado's Stuck Object Remover. Install the package file into [documents]\Electronic Arts\The Sims Castaway Stories\Downloads, and use it according to the instructions at the website.