Best GA4 Setup for Multi-Site Nonprofit Coalition (Cross-Domain Tracking + Unified Reporting)

Hi all,

I'm managing GA4 for a coalition of three nonprofit organizations that operate under a shared umbrella. Each has its own website, domain, and mission focus:

• One focuses on youth development and teen programming
• Another leads neighborhood revitalization and housing initiatives
• The third provides community services like senior care, childcare, and recreation

There is also a fourth site that acts as the parent organization. It doesn’t accept donations or run programs directly but serves as a high-level hub that shares news and drives traffic to the three operational sites.

Goals for GA4 Setup:

• Enable cross-domain tracking across all four sites using GTM
• Be able to segment user behavior by site
• Track shared events (like donate_click, email_signup, etc.) and still attribute them to the correct domain
• Create a unified funnel for shared events
• Maintain a clean, scalable GTM setup across all sites

Questions:

1. Is it better to use a single GA4 property with a custom dimension like organization_name for site-level segmentation, or 4 separate properties and roll up data in Looker Studio?
2. What’s the best way to implement cross-domain tracking across multiple WordPress sites in GTM?
3. How can we name and parameterize shared events (e.g., donation clicks) to keep tracking unified but site-specific?
4. Any lessons learned or examples from similar multi-site, multi-mission orgs would be super helpful.