Nobody should have to install an app to come on your trip. Everything works by link in a browser; the app just adds polish for those who want it.
Share one link. Friends open it in any browser to see the plan, vote and follow along - no account, no install.
Get the app for the live "Today" view, offline plans and the photo recap. Optional, never required.
Link or app, the plan is the same single source of truth - no one gets left out of the loop.