My family loves going here in the summer, and we always have a lot of run. With the change in ownership some things have changed. I know they'll be charging for parking this year ($5-$10, based on where), which isn't great since it is already a bit expensive.
Based on my own experiences, here's what I'd recommend;
Sunscreen with insanely high SPF rating - Put some on before you get here, then put more on after you change.
Teva's or other strapped sandals - you can wear these on the rides, and they help keep your feet comfy since you'll walk a lot
Cheap sunglasses – Dollar store are best, since you won’t care if you lose them
Waterproof watch – Only if you like knowing the time, it is very hard to find a clock here
Picnic lunch/Money – Most of the food sold in the park is very unhealthy and expensive, but you can leave a cooler in your car and go back to the lot to eat in any of the picnic areas, which are nice and shady.