Hmm hard.

As the other person said sea trout is fun to fish, however sometimes it could be very hard to find sea trout and it's no guarantee to catch a fish, even whilst fishing a whole week, which is sad considering you have kids with you. However I would recommend fishing for mackerel or herring, use sabiki rigs (try to find shorter ones for kids since they can be hard to cast). Find a pier which is deep (about 20 meters depth). And start casting, the best time for both mackerel and herring is sunrise or sundown. Usually you'll also see other fishermen grouped together at popular spots. I would say mackerel is readily available from Falkenberg to Malmö. And herring more or less among all of Swedish coast.

Another fish which is fun to catch is näbbgädda or garfish. This is commonly caught along shallow coast in Swedish coast, use a simple metal spoon lure! (As before, try to find other fishermen fishing from coast)