This is what I am trying with Zoee at the park...she goes crazy when she see's any dog (although, not aggressively)...I ask the owner if their dog is okay with other dogs and ask if they can meet. Once Zoee meets them she is fine and happy.
I'm not sure if you'd be able to do this with your dog, if he is showing aggressiveness toward them. Sorry, that's all I could think of.