The "Jardins de Tete Montoliu" is a large inside playground (interior d'illa) with a lot to space to have fun. It is also incredibly quiet.
The hill of Montjuic in Barcelona is a place full of surprises, there is a lot more to discover than one would think. Between all the famous sights such as Montjuic Castle, El Poble Espanyol or the Olimpic stadium you can find a place unknown for many people: La Caseta del Migdia.
If you haven't been yet, don't miss the opportunity to go to "Jardins de la Torre de les aigües" aka "la Platja de l'Eixample" (Eixample's beach) in Roger de lluria 56, it is close to Paseo de Gracia.
The Chocolate Museum of Barcelona offers workshops for children and adults. If you want to do something different with your kids in Barcelona and of course you love chocolate, then this is the perfect activity for you.
When visiting a city with kids we often need to take a break from the sightseeing and just sit and relax for a while watching the kids play. If you think this sounds good then I have just the place for you: "Plaça de Vicenç Martorell"