These two maps can be found on google maps if you just search: North Ryde NSW 2113, Lane Cove National Park.

The top map shows where were going to meet, which is the Lane Cove National Park Picnic Bookings area. Ive been there before, and theres like a lot of benches/information areas where we can wait for everyone to come.

In terms of parking: You can park inside the national park itself (i.e. near the Picnic Bookings area), but that costs $7 and is quite annoying to get to. The best place to park is shown on the second map by the two small red boxes near the top of the map. If you drive along Lady Game Drive, there are 2 parking lots that are free and (from when I was last there) have quite a few spaces where you can park. From there, you can just walk towards the meeting area/Picnic Bookings Area.