My DDs BFF moved away. Our families are meeting up at WDW, but the kids don’t know it. Both families staying at WL. Any good ideas on cool place to have the girls meet up for the surprise.
First off if the girls know that either family will be there I am sure it will be communicated. So is this a surprise trip for the girls as well as a surprise meet?
Maybe bumping into each family at the food court can be a fun thought. Have a meal reservation for both families one big table.
Oh I have a thought, create a scavenger hunt that both will end up at the same place.
I recommend a video just for fun: on youtube, look up videos from Bosox2001, and watch the Family WDW trip #4, where they meet up with friends at the airport. Really sweet! 
My DD knows she’s going, but not that the BFF will be there. The other family’s kids don’t know they are going nor do they know my DD will be there. I was even thinking that the boat launch at the WL might be fun.
Lots of fun places to have a surprise meet up at WL! Boat launch would be fun, or the bridge over the water in the lobby, in front of the geyser, the beach, the totem pole of characters… Can you tell I love WL?! There’s also a cool little nook on the 2nd floor with couches that overlooks the lobby and the room with the trains at WLV (the Spike Room?) Can’t wait to hear how it goes!