The flies are normally hectic during summer (I went in Feb and they were insane), but if you go a bit later they're almost non-existent (I went back in April for Easter and it was fine). The underground bunkers you mentioned are probably the ones on moreton. They're a lot better than the ones on Fraser.
Please don't ever conform to the cringe child friendly narrative that 4wd 24/7 do. I love the swearing and shit talk as well as the shananigans you get up to in your vehicles. Without any of that it's just weird and kinda cringe.
