I think doing a "Whiteout" would be better, where people only shop at pro-humanity or mom n' pop stores. Costco, Winco, ect. People must spend money for their necessities and to enjoy life, but if that spending can always be directed into the pockets of decent people rather than Bezos, that would be far more impactful than a day of blackout.
In that vein, I think incentive programs to switch people would be ideal. Something like CostCo giving a free membership if you buy an amount of goods equal in value, and a free pizza/rotisserie/hot dog(s) for buying $15 of stuff.