Count me as a maybe. I would love to attend but it's going to be a week-of decision I think.
Which parking area? Regarding dogs, the ONLY place I think you'd be allowed is Waterworks. In most places, the bike trail generally runs the stream. The trail and the parking areas (Stonecliffe, Gring's Mill, Red Bridge, Rebers Bridge, Palisades, Stilling Basin, etc.) are all considered to be county parks where NO PETS are allowed. Likewise if you plan on using the trail to travel the stream you'd be running afoul of the law with a dog. Not saying you wouldn't get away with it, but.....
So if dogs are a requirement, you could look into Waterworks, I've seen lots of dogs there, it's on the opposite side as the trail, and the trail is pretty far away from the stream there anyway. I'm not sure if you'd want to get permission there for an event like this or what. It is a dirt/gravel lot, wooded. Private enough I suppose, but could be a muddy mess in a rain situation. It's also back a hard to find gravel/dirt road so giving directions would be a little tricky for those who aren't familiar with the Tully.
I'd add that the whole length, from the dam to the mouth is stocked on the 9th. And the lower end, below the special regs, does fish pretty well in the fall, it doesn't seem to get fished out right away like after the opener. Not saying to go there, just that it's an option.
Aside from the dog situation, I'd think Gring's Mill or Red Bridge would be nicer areas for an event like this than would Rebers, Palisades, or the Stilling Basin. Rebers, for instance, is a small lot with heavy non-fishing traffic. One or two cars, not a big deal. But if you're gonna start having upwards of a half dozen cars it's gonna be a mess with not enough parking spaces, etc. From all of them, you can fish close, or jump in the car and drive to other areas.