We also used Barcelona Day Tours for a 1/2 day tour pick up from the airport on arrival day. We are a family of 5 and had 3 boys with us under age 12. It was a wonderful day and even arranged skip the line passes for us at several places. We also used them for transport from hotel to ship and from ship back to airport.
In Rome & Livorno we used Tuscan Heart Tours...I highly recommend them!