Not that it is much help to you with your little one but my DH sleepwalks when he is stressed and really tired (the combination is what does it). Last time he slipped off the top step (of 15!!!) and scraped his ankles on the bannister. It is a little worrying so we ensure the external doors are all deadlocked (he has previously walked out of a unit while sleepwalking and woke in the stairwell) just in case.