advice on taking German Shepherd camping in TT with kids?

I agree with Flapper, ToedToes and others. "Wait until he matures" is often a recipe for disaster. You need to have been working on training and socialization from the day you brought him home (maybe you have been). "Waiting until he matures" is akin to waiting until a human kid is 25 before you take them out into the world or start teaching them manners. By the time maturity occurs you're so far behind and have missed so many critical time points it's difficult to impossible to make up.