C.S.
L.,
At this stage in the game he doesn't have the skills he needs to be his own advocate. That's your job. Start talking to him on his level about whats happening and reassure him. If this problem with other kids persists jump in and help your little guy out by showing him the right way to handle it. He's not a coward just a little boy who doesn't know how to cope.
If you show him what to do he will pick up on it little ones watch everything we do.
Just give him the love and support he needs and he will be fine.
Good Luck
C.