RSVP here: ourbotanicalworldopening.eventbrite.com
For reservations it's first come first served, currently it's set so that people can register for 1 ticket at a time - but they can register for additional tickets. QBG encourages PWP members who are attending to RSVP and bring their membership card.
The event itself is free, but there is garden admission. PWP members all get free admission to the garden, but non-members will have to pay garden admission, which is paid at the gate upon entering. Parking is $6. Cars would need to be out of the parking lot by 8:30pm.