If you haven’t been to the East Bay Vivarium, add it to your list. Already a fan? Consider superfan status; you can have a little piece of the Vivarium brought to your house in the form of their traveling reptile program.
I recently attended a 4th birthday party that included a backyard show of creepy critters, and I was truly impressed. The demonstrator was full of age-appropriate information and humor for the kids. He invited the birthday boy to co-star in the show and backed off with grace when the newly minted four-year old was reluctant. A willing first-grader stepped up for the duties.
The show included a frog, a chameleon, a scorpion, a tortoise, a tarantula, a frog, a snake, and a huge kimono dragon, I think, but I wasn’t able to see everything as my own four-year old refused to watch any of it.
The entertainment lasted about 45 minutes, and all of the guests were completely engaged, with the exception of my stubborn daughter. This seems like a good choice for all ages, three and up (through adulthood!), and you can read pricing details on the Vivarium website.