Each pax has to be checked in individually. With the app only one person is signed in at a time. You could check your daughter in and select text or e-mail for her boarding pass, and have it sent to your phone.

Print them out. My wife (companion) and I both have phone/app and as long as it's reasonably easy when I check us both in (at home, at office, at hotel, at airport) I print us both out and put my phone in my pocket.