Bill kinda beat me to it but I think you should try for Sunday instead. Here's why.
Firstly, there is no rhyme or reason to crowds at this park. The whole "It may be less crowded thing because its Sunday/Easter/etc" thing does not apply here. In fact, I feel like Sundays are busier in my experience.
There are no events listed for this weekend on the website
or Facebook page
(other than the week-long Spring Break thing they're doing and "Talent Auditions" on Saturday) and no BAF specials other than a general all-April-long BAF for $15.99 thing that I can see in the app which shouldn't necessarily have a substantial effect on crowds either day this weekend.
So, based solely on the weather forecast
, I would go with whichever day you think the weather will be better for riding Ka and Toro. In this case, as of right now? I'd pick Sunday. Why? Saturday has crappy weather all morning and cloudy weather all afternoon which could lead to no one showing up which could lead to the park closing early which is not out of the question at all for this place. If people show you'll have nothing to worry about but with that forecast it'll be a crapshoot.
Alternatively, Sunday has rain in the morning for a shorter time period and will clear up and looks like it will be a nice afternoon with less rain and wind. It will be more crowded Sunday, but if you're traveling far, I think the better chance of having a good day is Sunday.