I think it would be best to do three sprints, two week and a half sprints and one week sprint. The reason would be to get a lot done in the first two, while allowing for some room for error, and then banging a lot out in the last week.
The minimum viable product will have the start screen, bear moving in our level, the text added and playing correctly, the end screens made and triggering properly, and the textures placed in the level well.
Sprint 1: Make sure all the writing is done and finalized, finalize level design, work on start screen
Sprint 2: work on end screens(trigger boxes), the bear's movement, and placing textures in the level
Sprint 3: Finalize end screens, place text in the level, and finalize the HUD. Make sure everything plays correctly and everything.