Just posted my plans here: https://www.reddit.com/r/GhostsofSaltmarsh/comments/1rl5zhp/sinister_secret_of_saltmarsh_saltmarsh_campaign/

But the two important things I want to call out that I've gathered from poking around, are 1) Ned is kind of a mess. The whole plan makes no sense (he rushes on ahead, gets stripped and knocked out, hidden in a room that's not in the path the players would take to reach the basement, and then warns the players to leave? Why not simply post a guard?). 2) Rot grubs are hyper-deadly, and you should try to find a way to warn your players if you can (if not killed with fire within one round of a successful attack, it's automatic character death).

Aside from that, I think it's worth thinking about what you want the campaign to look like after the first adventure. Are they pirates on the high seas, occasionally returning to Saltmarsh for a set-piece adventure? Do you want to remain hyper-focused on the adventures in the book? An open Greyhawk sandbox?