OP didn't ask ya'll's opinion about her plan. They surely have a reason to want to contact other parents, and that is fine!
OP-- I do agree with prior posters on asking the kid to be the connection, though. I have a MSer and it is common for another kid to ask my kid for my phone number ("My mom asked me to get your mom's number") and I subsequently get a message from the other kid's parent. I like it when people do that-- you shouldn't hesitate to use that mechanism.
In terms of the directory, all of my kids' schools (ES, MS, HS) have one as a way of getting us to join the PTA. I'm not certain, but I think that if you don't join the PTA, you don't get access to it. But you can join anytime and the signup process gives you a link to the directory. So you might search for your school's PTA information and see if they do it that way (I think the directory is called something like A to Z?).