Meta plot suggestions needed

[Exodore]

I've just been asked to run a short campaign over the summer and would really like some suggestions for a meta plot. I'm trying to come up with some stuff on the fly and spontaneous creativity is definitely not my strong suite.

So far, what I think I'm going to do is set the game in LOTR-Middle Earth within 50 years of the War Or Wrath (the beginning of the 2nd Age). The land is in turmoil... half of Beleriand has sunk into the sea, the inland sea of Helcar has been mostly drained and the lands from the north east down through Mordor have recently arisen from the drained sea. The Ainur are no longer active in Middle Earth, a large portion of the Elves have left, the Edain have left to establish Numenor, and the Dwarves are consolidating in Moria.

It seems like a fun place for players to adventure... but, now I'm struggling with the important parts... the actual adventure/plot... :(

Any suggestions are greatly appreciated.

[Shiroi]

I'm not impressively familiar with the setting, surprisingly, but I feel the time is ripe for a usurper to attempt the throne of the dwarven king while monsters afflict moria from the deep.

You have a three way fight with life and rule on the line, do you back the legitimate king, a generally fair ruler but who has lately been raising taxes without explaining the cause? The illegitimate usurper, who by all accounts is a famed adventurer in his own rights and believes the king to be corrupted in his old age? Regardless, don't allow the miners to be needlessly slain by the denizens of the darkness.

[Shiroi]

Alternatively, follow the elves on an ocean faring adventure. Sirens, deep sea aberrations, ghost ships, pirates, will-o'-the-wisps, and more, plus fighting for who will be captain after this one dies or a mutiny occurs.