As mentioned before it all depends on the wrestler.

When our oldest son began wrestling, we attended a tournament our club was wrestling in. (At the time he was not quite 6.) That way we could explain a few things to him as they were going on. Even the simplest things can seem overwhelming, (checking in before you go on the mat, putting the leg band on, shaking your opponent's hand and so on). All those things can be explained at practice, but for a young wrestler competing for the first time, it can all be very intimidating.

His younger brothers grew up going to tournaments, so to them it was old hat when they started wrestling.

Maybe have your boys wrestle in a novice tournament for their first time as well.