Weston Gardens would be a good place; there are so many.
However, one thing to keep in mind: my wife and I were at Weston today from about 3:00pm to 5:00pm; it was quite muggy already this early in the year -- uncomfortably so after about an hour.
Whatever might be planned for a Meetup from now on may very well have to be early evening (like the function you mentioned at the Botanic Gardens)--at least after 5:00pm, or else we'll wilt like petunias, and then many of these places are closing.
Plus, for settings like that with lots of shade and bright sun contrasts, the light from 11:00am to 5:00pm is extremely hard to work with. My useful shot ratio was way down today.

I sound like I'm getting old. :oops: