I´m not trying to be negative here but dust bunnies have an unpredictable quality. That may be fine for playing but from the preparedness angle it wouldn´t be too good. As the alternatives are cheap and usually readily available it may be better using them. I confess that I went through my dust bunny and dryer lint phase before I came to this conclusion.
The sawdust with wax would require a flame to light. The sheets would pretty brittle so don´t make them too thin. When are ready to deal with these limitations it could be fine.