Is this place safe for swimming especially for kids.

I agree Spanish Flat was a great area to go swimming for kids. The bathrooms were way cleaner then those at Putah Canyon.

Yes, there's areas in camp grounds that are great for swimming and larger water areas like Spanish Flat with typical swim area and deeper where boats and innertubes go. You can find coves or if on a boat, anchored out in the middle and swim, water isn't cold, great swimming

We were at Spanish Flat and the swimming was safe, no lifeguard on duty tho