Don't kid yourself. Grocery store executives are doing just fine for themselves. Donating does not make life any better for the front line workers.
If you want to help, support your local independent stores and avoid the chains. I know that's not practical for everyone and can be more expensive but better conditions for workers doesn't come cheap.
Even for the millions-paid CEOs it doesn't end up much when divided out among all the workers.
You can do much more for retail workers as a customer by not being an ass and by doing things like putting things back where you found them instead of leaving eggs in amongst the produce, etc.
If you want to help, support your local independent stores and avoid the chains. I know that's not practical for everyone and can be more expensive but better conditions for workers doesn't come cheap.