In Blender, good enough low poly characters, with say around 250 polygons can be made in 5-15 minutes, including rigging. Sloppy animations, a little longer.
Then the only problem is your complete lack of experience with the engine. If you have a 15 days deadline, then it’s going to be a little difficult, but not impossible, since you cannot really rely on the forums for an expedite answer to any issue you may encounter.
Good luck.