Thank you, everyone, for all the suggestions. I'm a big, awkward dork at the best of times, and all this playdate stuff is new to me, so I really appreciate the input. I emailed her and asked if they were still interested in a playdate "sometime this week" (I figured mentioning tomorrow might put her on the spot), explained our house was a construction disaster zone, and suggested we meet at a park. And she emailed back and invited DS to their house for tomorrow. So all's well that ends well, and next time I'll put on my big girl panties and email sooner.