Near the beach at Milne, there's usually a few GBH's a little closer as long as there aren't off-lease dogs around, but if there's one at Too Good, it'll like allow the closest approach.
While you're up that way, try Mackenzie marsh in Aurora. I believe it's Aurora sideroad & Yonge. I've had the Green Herons fairly close (they were walking on the road when the road was closed during construction).
I've never tried for a trail thru the southern portion of Milne. There might be access via Camp Chimo, but that's private property.