Are their bathrooms?

Yes

There are plenty of bathrooms around the park, especially by the playgrounds, if you cant find one, then just ask someone

Yes there are bathrooms through out the park. By skating ring ,play grounds, and Shmorgishborg

There are public bathrooms at the LeFrak Center at Lakeside, right next to the skating rink.

A few public restrooms and port-a-potties are around

They just opened one near the lake but it's almost never open.

Additionally there are public bathrooms at the Lincoln Road entrance.

There are bathroom that are hard to locate if you not familiar with the park .

Yes their are bathrooms

Yes, in many locations. Plus there are portable toilets.