It is open to the public
I don't know when the splash pool closes for the season but I do know it's not just for residents of Williamsville. Our son and daughter-in-law reserved the pavilion for our youngest grandson's birthday party. And they don't live in Williamsville. Neither do we, nor any of the guests. Great park!
Anyone can go. No resident ids needed, it's free. I'm pretty sure it is closed since all the lifeguards are college students but not sure.
Thanks! Your answer is awaiting moderation.