Why not just make a film on your own in 48 hours instead of paying money to do the same thing?
If you do it on your own, you won't participate with a shared community of others doing the same thing, where you can perhaps meet new people in your area who are interest in filmmaking, you won't be competing for nice rewards, and you likely own't get your film screened in a theater! There's no reason to subject yourself to the stress, exhaustion and hard work of getting something done in just 48 hours on your own!
If the schedule is like the 48 hour film fests I've done, this should be your tentative plan. Ideally you will have three "teams," a pre-production/writing team that will go to the kick-off, get the required elements (character/line/genre/prop/etc.) come up with the story and script, then a production team that will shoot the movie, then a post production that will edit. That way you won't have any one group stretching themselves too thin by trying to work throughout the full 48 hours, you can start to get footage to editors earlier in the day, they can already begin work on effects if needed, etc. That's ideally though, and may not be realistic.
You'll want to have several locations available to you for shooting, already planned out in advance, all located relatively close to each other to minimize travel time. That way you can pick a couple or one to fit what is required of you. The simplest is to shoot at one location so you can maximize your time, but shooting at more locations can look more impressive.
Here's a tentative schedule:
7PMish (or whatever the kick-off time is) get required elements
7PM-too late at night - send someone to buy/find any required props if need be, come up with story/script (KEEP IT SIMPLE AND STRAIGHT FORWARD, IF YOUR GENRE IS THRILLER, DO A THRILLER! HORROR, DO SCARY! This isn't the time to try and get fancy or overly thematic or meaningful! Just try and have fun with it!)
SLEEP
7AM - fill team/actors in on story/plan, begin shooting as soon as possible
8AM-around 8PM - Shoot the movie
EAT SOMETHING
9PM-import footage to computers/editing programs, organize, some editing
Hopefully get some GOOD SLEEP this night, you will want/need it.
7AM-5PM EDIT EDIT EDIT
5PM Export. Leave time to export, because it will take longer than you anticipate and you want to give yourself time in case of unforeseen problems.
6:30PM deliver "finished" film, whether you are dropping it off or uploading it or whatever
FEEL VICTORIOUS, EAT DINNER, SLEEP EARLY
This is more realistically what you can expect if you don't have a large team and are doing everything yourself or with a very small core group:
Get required elements, gather with team, spend too much time trying to come up with/agree on a story because too many people are providing input, agree on shit idea, realize at 12AM after team goes home/falls asleep that you and your main partner need to come up with entirely new idea that is decent and logistically doable, but half-baked because it is getting late and you really need to sleep and it is now 3AM so you go to bed. Get up early, fill in team, but some of your team will probably be late, a couple may bail on you even. Hopefully you have worked with some of them before so you have a shorthand and can work efficiently. Sometime in the mid/late afternoon your lack of sleep will catch up with you and you will feel brain dead, like you can't function anymore. Just push through it and you will get a second wind. You won't be able to do much editing this night because by the time you are back you will be so tired you are getting delirious. Best you can do is get things imported and get some things in the timeline. You'll get up early and edit your ass off, you'll feel well rested and like you have plenty of time (12 hours? Easy!), but you'll still end up being rushed by the end, you'll miss a couple silly obvious things in the edit (like a boom in a shot, audio problem, shot without color correction, etc), but it won't be a big deal. You may be exporting in a laptop on the ride to the drop-off to make the time. You will sleep like a king/queen this night.
You'll get stressed out, you'll feel like your movie is shit for most of the shoot/editing, you'll be tired, but somehow it will still be fun, and damn if you won't feel like you really accomplished something when you turn in that your movie.
Which character choices in particular?
lets just say that because of their back story, and external events, if we get to do a season 2 it will make alot more sense 
