So how do you feel about parents asking you about handguns in the house before drop off playdates? It's not nonequivalent right now.
I feel fine about that because it is asking me something about my own house, rather than asking me to go out and ask my other guests for a list of their social contacts. Like I said, it is totally fine to turn down invites where you don't know all the other guests, even outdoors ones with 1-2 kids. That's legitimate and understandable. Asking for a list of who other families kids can play with, or whether mom or dad has to interact with coworkers or the public, is unreasonable to me. But you're right, "I don't know" is fine. I'm not obligated to do more and am not going to.