ok kids are 2, 4 and 6. we do not spank
one example:
went to grocery store last night. got kids 'special' cereal(chocolate)

as a treat. put it on top of the fridge. this am got up to pump. fixed kids waffles and put them on the counter(they can get the yogurt themselves). i was pumping when they woke up and told them to go eat their food, at the table. come downstairs nad somehow they got the cereal off the top of the fridge nad between the 3 of them and the dog they ate the WHOLE BOX
another example:
a few days ago i was pumping(yes they wait until im pumping) and i told ds (2) to go wash his hands in the tub and come back. next thing i know they have flooded the bathroom

all 3 got IN the tub and splashed water all over the floor.
they know i am pumping and i always have stuff for them to do(show, coloring, play dough, etc) so idk why they make messes

but they know until im done pumping they are "safe" and then they get time out, have to clean up their messes, etc.
how do i stop this behavior???

should i just make them sit with me while i pump until they learn to behave?