Two-tier nonprofit, with explicit separation
The cooperative does not operate its own DAF. It contracts as a service provider to a chartered sponsor that holds a §501(c)(3) determination. The DAF sponsor receives the brand's cash contribution and issues the tax receipt. A separate operating §501(c)(3) (the Sponsor 501(c)(3)) holds the donated gift-card or Coop-IC inventory and coordinates POS adjudication with the cooperative under service contract.
This is the architectural lean the counsel work-stream has converged on (master spec §6.2.2). Two-tier DAF + Sponsor gives the most tax-defensible structure, the most operational separation between charitable receipt and program execution, and the most existing case-law support — over either a single sub-entity or a sister-foundation pattern.