Barcelona Day Tours are excellent. We've used them several times.
Otherwise, getting to Sagrada Familia is easy. Taxis are not expensive in Barcelona. Tickets for Sagrada Familia, if not bought through Barcelona Day Tours, can be easily bought online via the basilica's app. You'll want to spend 2-3 hours there.
Seems feasible to me to see Sagrada Familia on your own in the morning, return to the ship for lunch, then join your 2:30 tour.