I agree that a certain amount of physical contact is OK. But if the criteria is ..."as long as the player doesn't feel intimidated"....How can you tell...a kid may just clam up. That's why anything on the agressive side needs to be modified. JMO
I have the pleasure of officiating dozens of youth games each season at the younger age groups (under10). I will, without hesitaiton, flag a coach for grabbing a players face mask. Coaches can rationalize it all they want. It is wrong. If you cannot find another way to get your players' attention maybe you should consider another avocation. I make the call USC and let the coach know, one more and he's in the parking lot.