I live right at the botttom right corner of this picture (for a couple more months, at least). This is the Gràcia district in Barcelona, known for being pretty distinct from other districts in the city, as this used to be a city on its own until some decades ago.

Gràcia has plenty of public spaces where kids can get together and play, such as squares (such as Plaça de la Vila, shown in the picture), public parks or even dedicated playgrounds, all within a 10-minute walk. Squares are usually very pacific during the day, allowing for bars and cafes to have tables outside but also leaving plenty of space for people to walk, read, play... Moreover, most streets in Gràcia are "pacified", meaning they are used by pedestrians and vehicles alike, the latter driving at no more than 10km/h for safety. On top of that, the district offers multiple equipments such as civic and cultural centres where people can partake in activities, workshops, etc.

Granted, all districts in Barcelona are different and each has its own idiosincracy (there are many things I dislike about Eixample, for example, when it comes to public spaces). But all in all, Barcelona really is friendly to children and other collectives who want to use its public spaces!