To keep them home, you may want to make your yard more 'chicken friendly.' A big lawn is nice, but they also need spots to take cover or shelter. Shrubs and bushes are good places for them to duck for cover. Berry bushes would help provide forage, as would a few compost piles. The way your yard is now, there is very little to keep a flock occupied.
wandering chickens - Page 2
What I have found, if you don't let them out all the time, then when you do, they tend to stay closer to home base. The more you let them out the braver they get.
The big thing, is they love to dig in loose dirt, and they can cause very expensive damage to neighbor's gardens. You need a fence.