This is an ideal beach in many ways. Free parking, public restrooms, easy access to the sand (park right in front of it), grassy area, picnic tables, pier, restaurant, and it's beautiful! Waves are generally small which is nice for young children.
I am often surprised by how cool it is. Cool as in cold. The sun can be shining but with the moderate temperatures of Santa Barbara and a cool wind, it can be downright cold. Also surprising is that you won't see the sun setting over the water, like you might in California. This is a south facing beach, so it sets over the hills of UCSB to the west. So take layers and enjoy!
I grew up at Goleta Beach, and I've always loved it. It's less crowded than a lot of the downtown beaches in Santa Barbara, but only 15 minutes up 101 from downtown. UCSB is within easy biking or walking distance. There is a great playground for kids (ages 4-8, probably, though mine were 18 mo and 2.5 when we went and they enjoyed it) with playstructures, sand, swings, etc. It is not enclosed, so that's the one downside, but there are lots of benches and it's pretty easy to see the kids from all sides. It is right on the beach, so you can stroll down there to play in the water or collect shells. Beware that there's a lot of tar, especially after a storm, so just be prepared with Goo-Be-Gone or something else to take it off. There is a lovely restaurant there called the Beachside which tends to be have a lunch and dinner rush, but the view is well worth it. There's also a pier that you can stroll out on.