I like working with kids, until they run through my yard

I have limited internet access this week before my wireless is set up on Monday, so unfortunately I can't update much on the new house yet.

Right now, the most pressing issue is that a bunch of neighborhood kids have taken to running through my yard. There are two boys, both about 14, one on a bike and one running. They know they're not supposed to cut through, because my landlord has explicitly yelled to them that she's going to have them arrested (she's fantastic). I've yelled at them a few times myself, but it doesn't seem to help.

I have two ideas that I need input on.

Put a spike strip across my yard. May be an issue for the runner, but it will help with the kid on the bike.
Put a clothes line across the yard.

(The kid doesn't actually wear a storm trooper costume, but this is the best picture I could find to explain it)

I may have to resort to the clothes line because I'm having trouble finding a spike strip. Thoughts?