My ds is 3.5 years and is grazer. Snacks have become the main flashpoint for tantrums. He also has a new sibling and constantly asks for food (despite good mealtimes). This is really tricky when feeding a newborn.
He has taken to using his step to get snacks. So today I have set up a low level snack cupboard with only healthy snacks - rice cakes, fruit etc... and little bowls to put them in. When starts his whining I showed him and explained it is his cupboard to prep his own snacks. I thought by giving him responsibility and trust it might prevent problems.
Those who say their child only has two snacks a day - for this little boy that would not realistically work.