Your free ranging situation sounds similar to mine. I have a small herd of dairy goats and keep them without any fences, and they wander about a bit, but they always come back when it's milking time or treat time, and if there's a comfortable undercover place for them to go at night that's close to the milking area and treats, then they go here at night, and then go out browsing during the day. To do this successfully I think there needs to be a time of adjustment for them to get used to where home is, and where the treats are, so if you can set up a small fenced area with a shelter for them, they can stay there for a while until they've settled in and get used to getting treats at certain times of the day.
Kidding time can be a bit more stressful with free range goats, and can involve a lot of observation of them to work out when one is going to kid in the next few hours, and observing which direction she goes off in. Alternatively at kidding time, one free range goatherd I know keeps the goats that are very close to kidding in a paddock near the house so he can keep an eye on them - this is what I'd like to do eventually.
Free ranging a small herd doesn't really do much towards clearing brush, and higher numbers will lead to them eating their favourite plants, leaving the rest, and possibly compacting parts of the land. Most people who want to clear brush will concentrate their goats over a smaller area, and then quickly move them on to another area by using portable fencing. I don't really mind that my goats are not clearing brush, as they are producing food and spreading manure on land that would currently not feed other animals, plus I love goats, milk, and cheese.