canadian pool regulation ?

i currently sort of manage a swimming pool and I'm kind of confused to a
specific issue. there is a member of the board that on numerous occasions
take his family in after hours and there are children ranging from 6-10
years of age and there is no licensed lifeguard on deck do to the fact that it is after my shift and the doors are locked, i was reading pool safety regulations and it says the occupier
which i think is me, is responsible for trespassers liability of safety,
which would be them, i do know of some occasions but it is the day after
that i realize they were there, so would i be legally responsible if some
kind of accident were to occur, because the board member does not listen to
me about this so what can i do legally to ensure that i cant be responsible because there is no lifeguard there, please help because accidents do happen