Hello,
There is a Barcelona taxi service that can provide baby seats and boosters (although a limited number) but unfortunately by law can only carry 4 people as with all of the licensed taxis. You could perhaps take 2 taxis if there are 2 adults travelling as it can still work out more economical than a transfer service. All the transfer companies that we have been in touch with do not seem to offer this service. Hopefully somebody has a recommendation for you. The other option is simply to take the airport bus service which is almost as quick as a taxi into the city, stopping at Plaza Espanya and Plaza Catalunya.
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