Hijacking this post to ask a slightly different question:
Does everybody have to be present at check in for all to be checked in?
One thing is checking in separately, as OP describes. Each one checks themselves in and meet onboard.
We plan for me and dd to check in all three while dh returns rental. We could do that last time.
I think this what people have reported not being able to do anymore (at PC).
I hope we will be able to, it feels so much more efficient