All great suggestions. Also, for peace of mind, ask which emergency vet they use and check out that facility as well.
We also include an unwashed T-shirt (one from each of us)that we have slept in for a few days so our smells are concentrated. Ask if someone plays with the dogs when they're turned out to run, and ask if there is a washer and dryer on sight in case of an accident so the bedding gets washed.
All my above suggestions have come from experience and grant me some peace when I have to leave my dogs. That said, I'm still a BIG baby when I have to leave the "kids".:o