time management and the unknown

Hi Brooke-
I am trying to plan out my day… but maybe I just need to double all my time windows for things? The thing is I work from home with my autistic child. Some of my biggest struggles trying to work from home are: I don’t know when he is going to need to go to the bathroom, do something no one thought possible that requires extensive clean up (it was an hour last time and involved 2 black widows) or have, say, a 5 hour tantrum. How do I plan around this? Not to mention the break in concentration. I know you say there are no excuses… but not figuring my way around this one (yet).
Thanks, Gina