Hi everyone, I'm the OP. Wow, this thread sure took an interesting turn!
I just wanted to thank you all for your responses and let you know I'm reading them all, albeit slowly from my phone.
Interesting that people jumped straight to my *dog* as being a risk factor, as that's something I hadn't even considered! With my particular toddler, my particular dog and situation I definitely feel the dog's presence in my back yard only made things safer, because I know he would instantly alert me to any danger, be it a person walking into the yard, another animal, or what have you.
My dog has never bitten or even threatened to bite any person or any other dog, ever. He barks a lot but otherwise is almost comically timid. The only time I can imagine him biting would be (possibly) to defend my DS. He's not an old or sick dog (he's 2) and he's ridiculously tolerant. On top of that my DS is really good about not pestering him, especially when he's outside because he's busy exploring!
So yes, while I acknowledge the possibility of him biting my DS, I'd say it's about as likely as a random person on the street biting my DS. Or even less likely, really.
However, what a PP mentioned about the danger of "friendly fire" did give me food for thought. I can see how it would be possible for the dog to knock him over or something while playing. So I am going to be cautious about that.
I'm not in denial about dogs. I was bitten by a dog as a child. I used to have a dog who, while she was a total sweetie, I would *never* trust her alone with a small child. I do think I know my child and dog well enough to trust the situation, especially when I'm within earshot, can walk to the window and see them at any time, and could get out the door literally within 30 seconds! Thanks to those who gave me the benefit of the doubt!
It sounds like aside from the dog issue, most people think sending DS out to play is fine, but obviously it would depend on the particular child and the setup of the particular yard, which is pretty much what I was thinking. So thanks!
PS. As for the gate latch issue, not really a concern for us at this point. Our guy would have to be at least a foot taller to reach that, and it's always locked, and he doesn't show any interest in latches yet. For him it's more about finding cool rocks to show me.