Summary: This is a fabulous B&B, even without the astronomy. And unless you're unlucky and get clouded out, you'll have an unforgettable night sky experience.
Some background: I am an experienced amateur astronomer, and stayed with my wife and kids (7 and 10). We booked both rooms, stayed two nights, and took the star tour both nights.
First, this is a great B&B. The rooms are very comfortable, the lounge has a great collection of books, games and movies (many on astronomy and sci-fi, to get you in the mood), and the breakfast is sumptuous and first rate.
Then, there is the astronomy. The most important thing in astronomy is the quality of the sky. You need clear skies, and the absence of city lights, and this site has both - which is why we came. It's only 35 miles from the legendary Palomar Observatory, the site of the largest telescope in the continental US since the 1940s. There's some glow on the SE horizon from Mexicali, but it's not bad.
The owner, Mike Leigh, has probably the best-equipped amateur observatory that you'll ever get access to. He has four superb permanently-mounted telescopes and operates them in such a way that you're never waiting long to see the next thing. He is both experienced and knowledgeable, and can explain astronomy to anyone. He has a real knack for explaining cosmic concepts in terms everyone can understand, and a wonderful sense of humor, too. My kids loved the sky tours, as did my wife and I.
And if you want to go the extra mile, he has a medium-sized portable telescope that you can rent for the night to use on your own - which I did.
As to some of the criticisms in other reviews: yes, there is a guard dog, and you will likely see it behind a fence and hear it bark, but it did not bother us in the slightest. After dark I did not hear a bark at all, even when I was wandering around on my own to and from the observing area.
Yes, it's possible that you will call and nobody will pick up; or you'll have to wait a little for the doorbell to be answered; but Mike and Caroline run the place by themselves and you can hardly expect them to be everywhere all the time. They are gracious hosts and have generously opened their home and observatory to guests of the B&B and anyone who wants to book a sky tour. When you factor in the quality, the hospitality, and the unique astronomy experience, this B&B is terrific value.