Mommies! Daddies! Teachers, too! Do the kids a favor. Do not make them watch "I, Leonardo: A Journey of the Mind," presented by IBM at 8 night on Channel 9. Better they should watch (at 8 on Channel 20) something truly fine, say, Walter Huston's acting in "The Treasure of Sierra Madre."

"I, Leonardo" is no treasure. It is a puffy bore.

Its cast sounds terrific--it's got Frank "Dracula" Langella, wearing long gray whiskers, in the title role, Richard Burton's voice, and Walter Cronkite, too--but the three of them are wasted in this pompously produced, dull lecture of a show.

It is drama-less and action-less and no fun at all. Faced with the daunting prospect of surveying Leonardo's mind in one hour of TV, Chandler Cowles, who wrote the script, and IBM, who paid the bills, thought it best to play it safe. They have invented nothing. Playing Leonardo, Langella doesn't get a chance to ride a horse, confront a prince or even smile at the Mona Lisa. All he gets to do is peer into the distance, dabble with damp clay, and then read various paragraphs from Leonardo's notebooks.

Leonardo, although very smart, blew it now and then. His frescoes rotted on the walls, he couldn't cast his giant horse, his flying machines didn't fly. Langella-Leonardo tells us that a dropped cannonball "passing through the atmosphere grows heavier as it falls," that the light from the sun "gives light to all celestial bodies," and that big clouds hold winds the way sponges contain water.

Because mere notebook readings make ponderous TV, and because the camera won't rest for long on Leonardo's drawings, this awe-struck show is padded with countless arty-somber shots of sunsets in soft focus, glinting running water, and Andalusian horses running in slow motion. Occasionally, stern-faced actors step up to the camera. "I am Giorgio Vasari, architect, painter and biographer . . .," intones Joseph Maher. "I am Niccolo Machiavelli," says Jeremiah Sullivan. All they do is talk.

"I, Leonardo" opens with a quote from Kenneth Clark: "Leonardo is a standing refutation to the comfortable belief that all great men are simple. No more complicated and mysterious character ever existed and any attempt to simplify him would run counter to the whole action of his mind." This show ignores that warning.

IBM, instead of peddling its computers, gives us Walter Cronkite promoting "quality education." The show has been dutifully endorsed by the National Education Association, the American Federation of Teachers, and other worthy bodies.