My eight are now about 8 weeks old, and I don't have any older chickens either. This week we just started letting them free range for a couple hours each day. They really love being able to run around. They have been living in their outdoor coop fulltime for about 10 days, and they seem to recognize that it's home. When they're out, I check in on them every few minutes to make sure they're not getting too far afield. So far, they've stuck pretty close to the coop - within about 40 feet or so. We have a lot of open space in our lawn next to the coop, and they really don't want to venture out into the open spaces. This tends to keep them from wandering far. They really like to hang out under the pine tree (also under the cars, unfortunately). They're relatively easy to round up at dusk - we just herd them toward the coop door, and tuck the stragglers in.
If you let them out, keep an eye on them periodically. They may decide to stick close to home. If they're people-oriented, it shouldn't be too hard to collect them when it's time for bed. You can always resort to luring them back with treats. If you work on getting them trained to come running for treats when you call, that will help you feel more in control while they're out wandering.