Reward tactics for non-reaction

What is the best way to solidify a non-reaction in a show-me-the-cookie dog whose breeding is to be on alert?
 
The story:  We are back at our cottage on a medium sized busy lake with a shore path which is open to all walkers.  Many walkers have dogs -- every size, shape and energy level.  Neighbors seem to be on a kick of pointers and brittanys who need to do a lot of fetching and leaping off piers.  So there are ambling dogs, jogging dogs on the path.  And racing, fetching dogs.
 
We literally live on the screened-in front porch with floor to ceiling screens at the very center. Every year I have to start over with alert-dog Zibi who just completed a quiet winter with not much action going by our door at home.  And with windows closed.  All this cottage action ... is too exciting.
 
After the first few days of too much barking, he becomes less reactive as he is consistently dragging a leash and I have a supply of treats for attention to me (and thus turning away from the screen).  At some point he starts just calmly watching the majority of walking and jogging  dogs.  And sometimes not even picking his head up off his paws.  Hooray.
 
And it is this non-reaction I need to now how to reward.  Mostly I give him a very soft "gooood booooy".  No treat as I don't want him to get up or start lobbying for treats.  I think I want him to go back to sleep.
 
Any thoughts?