Either is fine, but I prefer my laptop. When we sailed last December, I did check-in my MIL and FIL. I logged myself out, and then logged in with my FIL email and password. They did get the same check-in time that we did.
Our BIL & SIL were also linked to our reservation, They got a different check in time, but they were able to check in with us at the earlier time.