Glad you made it to Newport. That's where I live btw. So it was interesting seeing someone's perspective during the off season.
I do suggest going back during the summer. A totally different vibe as there are people all over the place. The sand won't be cold - in fact it will be hot. And I'm talking burning hot. Flip-flops are suggested for sure. And just so you know the water off the so cal coast is cold and can be as low as 50 degrees in the winter - so your little one definitely was brave when it came to getting his feet wet!
anyways I am happy you had a great time. Definite to on the harbor cruise. They will show you celebrity homes and the second half of the cruise takes you out into the ocean where you will see sea lions and maybe a dolphin or even a whale!