Your options, compared
- QR / link photo sharing (Eventoly): no app, no login, original quality, one album.
- Google Photos shared album: free, but contributors usually sign in with Google and it uses your storage.
- WhatsApp group: everyone has it, but photos are compressed and lost in chat.
- Dropbox file request: no account to upload, but it's one-way and uses your storage.
- AirDrop: instant for iPhones nearby, useless for Android and after the event.
Further reading: event photo sharing, Eventoly vs WhatsApp.