Family can be a pain, that's for sure. My wife has 3 siblings with no kids at home, and yet it's next to impossible to find a date when we can all get together for a holiday. It's a lot more work, but how about calling each one and discussing your plan. You could gently explain why it'd be nice if they answered emails— some of them probably can't imagine how much effort you put in the make this happen.
On the side, when you mentioned mummy dogs, I misunderstood and thought everyone brought their dog to be costumed as mummies. Might be a good plan...
On the side, when you mentioned mummy dogs, I misunderstood and thought everyone brought their dog to be costumed as mummies. Might be a good plan...