Try not to encourage this behaviour by doing things like oh it's ok it's ok, and stuff like that. the dog will think he's supposed to act like that and is being rewarded. I have a big chicken dog, and we just ignore her and the behaviour and I tell others to do the same. Makes a big difference. She's scared to death of gun shot and loud noises and we just continue on and ignore her.
Some adults she's leary of at first, and if they don't talk to her or look at her, she is soon in their lap.
i have a 4 month old male rottie he seems to be afraid of nothing outside my house
i dont baby him at all...i allow him to investigate EVERYTHING that will not hurt him...even if it means making him stand there and letting the garbage truck do its thing(he was scared of that at about 9 weeks old)...now he ignores the garbage truck
he meets new dogs and new people on a daily basis...i make it a point of seeking out dogs ,people and new situations for him to deal with...actually they seek me out when i walk him
IMHO doing all the work now will make life easier for me when he is 100+ lbs in a couple short months...