Family visiting Great Lakes TSC?

All he will need to show is government issued ID (like a driver's licences), and anyone else who is over the age of 18. Parents will have to vouch for any children under 18 if they don't have their own IDs. Since they are your guests, YOU are responsible for anything they do on base, if they do anything bad. Great Lakes is used to random people coming on to see their recruits in training, so it's not an issue to get one. But on some other bases, civilians can't get on unless they are physically escorted by someone in the military.