Is there any fee for entering in park also is there any swings and slides for kids i mean free entertainment for kids?

Yes to both. Once you pay the entrance fee everything in there is free.

There is a fee if you go to the main entrance and a free access at Alameda creek but not for kids unless fishing. It's usually free on weekdays. But if you go on the backside which is at Niles it's free and parking and there's also a playground near by.