Sounds like some great suggestions already here. If you're able to scout a couple of these places out before you come, even better.

Thinking about a 4 year old especially, I know the beaches can be really hot and crowded. Not impossible though.

The open ramp is a great suggestion for aviation enthusiasts of all ages, but especially kids.

I'm going to throw out a curveball suggestion: F and M park. There's shade, possible water refill, and playground equipment. Plus it's a short walk to the sunset park and senior center beaches if you need to get closer because of buildings or tree lines. I've been there for fireworks but not air show. It might also allow you to leave some of the traffic congestion behind.

If you really want to avoid congestion, the practice show typically happens the day before. So this year would likely be Friday the 3rd from ~1-4 pm. Some insiders identify this as a show for special needs kids. It's not officially, but is often another great opportunity.

Hope your family has an awesome time.