[JoeyP]

Ahh ...how are they on the playdates?
Do they bark there too or is it just on the lead?

What I would suggest is get a friend with a dog to help you out
Take them out and have you friend with their dog come to you from a distance
Have you pups see them and then quickly distract them with a treat BEFORE they go bonkers
Best way to do this is hold the treat in your hand so they can smell it but not get at it
repeat this a few times
do it again but let them see the dog for longer and longer periods
If they start barking you turn and walk them away in the opposite direction until they stop and then go back to start over

It's a long process but what you are doing is stopping the need for them to feel they have to go into alarm mode