How to handle neighbors who let their kids freeload in your backyard without asking?

We have friends who are neighbors and they never ask if there children can come over to play at my house. So whenever my family goes outside into our backyard, these kids come running over and just barge in. The parents never ask, will leave their home to run errands, and literally assume their children are “playing outside”. But in technically, they come to use my bathroom, ask me for snacks, tag along if we go to the park,...

Other families on our alley have the same situation, and basically we are being treated as free baby sitters. This family never invites other children over, never offers glasses of lemonade,...only takes.

This is such a problem that I don’t look forward to spring / summer simply because of this issue. We have a 6’ fence on the alley and aim to keep it locked. But the space invading kids will enter my property from an unlocked gate just to get inside.

HELP.