PP here - I realized I never really answered your original questions. If you look on the website, you'll see there are occasional special event nights (movie night, fishing derby, etc.) Doesn't look like they're very frequent but maybe they haven't all been planned yet. I don't recall there being many activities when I belonged there, but my kids were really young and we were occasional pool users, so I may not have seen (or been looking for) them.
The website also describes the various pools and their features really well:
https://www.reston.org/Parks,RecreationEvents/Aquatics/AquaticsOverview/tabid/269/Default.aspx
The schedule of hours is here:
https://www.reston.org/Portals/3/2017%20ParksRec/2017%20Pool%20Schedule.pdf