Early arrival to airport or day use hotel in Barcelona?

Hello everyone!

I was hoping for some advice from those familiar with Barcelona airport. We will be disembarking from a cruise in Barcelona and need to be off the ship by 9 am at the latest. Our flight departs from BCN at 3 pm. We are in Barcelona for 5 days prior to our cruise, so we don't feel the need to do another tour or further exploring during the time in between and just want to park ourselves somewhere until we leave.

I am deciding whether we should go straight to the airport or rent about 3 hours at a day use hotel near the airport. I don't know if we can check in and drop off our luggage and make our way to a restaurant/gate/lounge if we arrive at the airport at least 5 hours before our flight. Does anyone know whether we will be able to check in that early? If not, is there a good place before the gate to park ourselves and belongings? Also, through various credit cards and rewards programs we should be able to swing access to the Miro lounge for our family of 5 (3 adults & 2 kids; we may need to pay for 1 person). Is there any other place you would recommend hanging out at the airport other than that?

Thank you!