I've got a five year old Aussie Cattle Dog (a breed derived from, among other things, the Dingo), who loves my kids with his entire big furry heart. He treats them exactly as he should. That means that if my three year old is bothering him, he gets up and moves. If she follows him, he gets up and moves again. If she persists, he'll get up and move again, but he'll grumble this time. If dd is still provoking the dog, he will let her know, in no uncertain terms, that he is DONE with this game, by turning towards her and snapping. Not close enough to even touch her, but getting his point across. He is warning her that he is at his limit.
We went through a rough patch with DD1 where she would NOT leave the dog alone, and I almost ended up having to keep the separated all day, which would have been extremely hard in our tiny house. Patient, loving explanations about what is appropriate and what is no appropriate and a lot of "What do you think Baxter is trying to tell you?" finally got it across to DD1 that if Baxter gets up and moves, the nice thing to do is to not follow him and let him have his space.
If you're staying with a dog for a short time, with a child that has been known to pester the dog (or any other dog), my advice would be to keep them apart as much as possible. And as previous posters have said, don't leave your child alone with the dog, not for a second.
I don't think it's unreasonable to ask your brother to help you figure out how to keep them separated. I do think it's not entirely fair to ask your brother to banish the dog from the house for the duration of your stay. If it is that big of a problem, I would not stay with my brother. However, it sounds to me like the dog was warning your daughter that he'd had enough, that time he snapped at her. I'd simply stay with your child at all times near the dog and help dc learn how to touch the dog gently.
Also, I'd encourage your brother to make sure that the dog has a place that he can retreat to where no one will bother him... a den-type idea. Then, be sure that you keep dc out of that area, whatever it may be.
Best of luck!