Great idea. I second the idea of using lnbits. It can do most of what you're asking for. Also, no setup, per se, is required. Basically you can just spawn a sub account for the tipee and let them scan a QR code which brings them to that wallet. The mobile interface is very clean and easy and no install is required. I'd definitely start your POC with that approach and then see what if anything is missing. Likely you can implement a plugin to lnbits to fill in any gaps, or perhaps incorporate all of the onboarding functionality into a single new plugin for simplicity.