My players want a campaign out of my one-shot! HELP!

So a while back I had the idea for a one-shot based around the three little pigs (still serious) where the big bad wolf was some kind of demonic lycanthrope with a breath weapon. When some of the group couldn’t make it, they asked to do a sort of session zero for my one shot with an encounter. It went well! …for once in my life, maybe a little too well. Now they’re interested in a full campaign based around what they’ve seen so far! The crazy part is I don’t think they’ve figured out what it’s based on yet! So, I’m looking for ideas.

So far, after 100 years of no werewolves, two people transformed into hybrids at the tavern the party was meeting a contact at. A halfling (little pig) spoke of running into a big one last night at his home and is interested in hiring the party. They checked the rooms of the ones that thrned and found a map of around where the halfling (Al Bacon) lives, so they are going there next session first.

Along the way, they’ll run into a Tiefling girl named Red going to her grandma’s house. When she gets there, she’ll notice parts of her body aren’t quite right. Needless to say it’s another wolf, but this one seems to be able to shape-shift to resemble other people! The party can find grandma’s regurgitated body from the Big Bad Wolf earlier, as well as a note revealing the grandma’s mother was a blood hunter who helped make a deal with Malar the beast god to get rid of the werewolves for 100 years.

I’m assuming after that, they’ll go to the three halfling’s houses to make plans to fight the Big Bad Wolf when it returns. We’ll see how they strategize and what damage it can do to the infrastructure with its breath weapon.

That’s the short version of what I have planned. So, where should I go from there? Do I try to make it last longer? Do I make more werewolves? Do I go with the fairy tale theme? Do I call it quits after TBBW? 

Go full on Disney Fairy Tale.  So many story ideas.   Lots of singing = bards.

Creation Bards = dancing tea pots, etc.

Glamour Bards = the villain that sings a 'convincing' song that has good people demanding the blood of some innocent.

 Put in a Mermaid walking on land desperately trying to meet her prince.

The misunderstood 'evil' ice themed Materializer wizard (Griffon's Saddle Bag) whose sister wants to redeem her. Throw in an Snow Golem from ice wind dale.

And you absolutely have to have seven dwarves trying to find a cure for a human princess that took a bite from a poisoned apple.

What do you want to do? Are you enjoying DMing? Do you like the story and want to build on it further? 

If you are enjoying the story and the process of DMing it would be very easy to build on it into a larger campaign. You could either go the fairy-tale route and have the Big Problem linking all the stories together to be the walls between the Material World and the Fey Wild becoming "leaky" - if you want to continue it into a high level campaign. But personally since it is your first one I'd recommend keeping it small and just extending as such:

1) They defeat the Big Bad Wolf
2) Upon return to town reporting their success, they meet two factions: One that wants to hunt down and kill all the werewolves, and One that wants to create a cure for lycanthrope. They can choose to join one or the other but not both.

3) Hunter's Plot Line: They are sent on a few more missions to discover & hunt down some werewolves, during these quests they learn something is calling to the werewolves - summoning them to a higher purpose.  The hunters learn of a temple to Malar where high priestesses bringing together/organizing the werewolves into an army and trying to create a new Champion of Malar. The hunters want do destroy the temple, and bring the party in on the plan. Campaign ends with the party planting explosives while fighting off the priestesses of Malar / the champion of malar before having to escape the temple before it explodes and is destroyed.

4) Healer's Plot Line: They are sent on missions to collect rare ingredients to work on the cure, when they return they learn some of the werewolves that were seeking help have left having been compelled by some magical summons. The party is sent to follow the werewolves to see where they are going and discover the temple of Malar with the high priestess that is mind-controlling the werewolves. Campaign ends with the party infiltrating the temple to kill the high priestess and freeing the mind controlled werewolves to choose for themselves if they want the cure and live as humans, or to choose to live as animals in the woods. 

Interesting…

I had planned to work in a homebrewed version of a Beast of Malar. That could serve as Malar’s champion… unless there is a statblock I am not aware of for such a character. There were several other were creatures I was going to work in via groups or adds based on how many people show up for my sessions when I do them. 

The only thing with choosing whether or not to kill or cure is the monsters will likely be the same, and I don’t want to give the illusion of choice. In addition, as I implied above, most of these enemies are in groups, so I’m not sure you can cure one without either killing the others first or risk the the one you cure being infected again so soon afterwards.

Regardless, you’ve given me more to think about, which is good, & I appreciate it. Thank you!

Make a note of who strikes the killing blow to the big bad wolf.

On return to the village (or whatever happens after the fight), the party encounters a group of lycan hunters who ask them for some quests to destroy the last of the lycans once and for all. Whilst they do so, whoever killed TBBW starts getting visions, where they get guilt tripped by two mourning children for killing TBBW, which slowly become more accusatory, but then take a dark turn as the next full moon approaches, and the two children which mourns the big bad wolf's corpse in the dream turns to face the character and tells them "There will always be a big bad wolf."

The character will begin to become a lycanthrope. Religion checks realise that these are the gods of fate, the Brothers Grimm. The party by now will already have given the lycan hunters enough tools to destroy all werewolves at the next full moon, and now one of them is a target.

The quest now shifts to curing the character, or stopping the lycan hunters, or both. Make it one of those "If you can't stop it by midnight on the full moon..." type deals.

For a light-hearted (but ultimately dark) addition, have a recurring character who alone witnesses the PC briefly transforming, and runs to tell the others. Each time, they will see the PC after the event, looking normal. Eventually, they disregard the lone character. Later, the character will try to raise a warning, and they will ignore them, to their dismay (the boy who cried wolf).

Bonus points if the PC transforms for the latter part of the final session, and the character is the first of their victims.