The check-in might be at the airport already. If not, you can still drop your bags at the port and then leave. Nobody will force you to check-in.
When you land at 9 am, you might be outside with your bags by 10 am. So with a waiting time for the transfer bus (and maybe a check-in at the airport) and a 30 min bus ride you might arrive at port by 11 am.
There are plenty of taxis available at the port. No problem to get one.
As for the Sagrada Family you need an online appointment for a certain time. Otherwise you may end up in a long line and never get inside.
steamboats