The Spanish love their children – and everyone else´s. You will hear the word ´guapo´ (guapa for girls) used a lot in Barcelona. It means good-looking and can be used just as easily with children as with adults.
Kids are very much a part of daily life, so it is perfectly normal to see children of all ages in bars and restaurants late at night with their parents, grandparents and friends. This is partly because children are naturally included in everything and partly because the Spanish eat their evening meals very late!
Although the Catalans are supposed to be more reserved than the rest of Spain, you will find Barcelona to be a very child-friendly place. Spanish kids are not shy, and your children will grow accustomed to interacting with friendly locals who speak with them.
The downside of the natural and constant interaction the Spaniards have with children is the tendency for strangers to feel perfectly comfortable disciplining your kids or telling them what to do. It can be annoying, but try to take it all in stride. One thing you may notice about Spanish parents is the tendency to be much more emotional with their physical interaction with children. This means that love is shown with large embraces and many kisses and displeasure is equally clear, with more than a few impromptu spankings being a normal part of the streetscape.
Children are safe in Barcelona, on the whole, although the Spanish are very attentive parents and it is very unusual to see a child out of sight of their caregiver. Generally, people watch out for kids and are extra patient when it comes to giving way in the street or being stuck behind a little person who simply must examine this particular paving stone for ten minutes.
There is plenty for children to see and do, and younger children will make friends very quickly (even if they don´t want to) as the children of Barcelona assume everyone under the age of 12 wants to play, for as long as possible.
Older kids (13 and above) will need to be able to speak the language a bit, or go to a school that has a high expat population in order to avoid feeling isolated from the local teens. As for weekend activities, there are plenty, and it is a safe enough city that you can feel comfortable about your teenager being out all day with their new friends. They will probably spend a lot of their time on the beaches, in the parks, or just hanging around the pedestrian malls. This last one is a perfectly acceptable social practice. ´Loitering´ is a national pastime and neither you, nor your children, will be considered a local until you learn its art.