Washington ? Every once in a while something happens that sorely tests the fundamental goodness of the American people, that challenges us to rise above the petty and to walk a righteous path.

And so we are about to be tested: Royal newlyweds Charles and Camilla are coming to visit.

Be nice.

No references to those intercepted phone calls in which His Royal Highness fantasized about being one of Camilla’s feminine hygiene products.

Nothing about how Camilla compares with Princess Diana, the first wife, looks-wise.

And no snide comments about her giant hats; that’s the style for proper Englishwomen of a certain age.

All that would be rude.

Besides, the three-city, weeklong itinerary of the Prince of Wales and the Duchess of Cornwall is notably devoid of most anything frivolous, anything that would recall the high glamour of Diana’s penchant for celebs and shopping and the low comedy of multiple royal adulteries.

According to a news release from the Prince of Wales’ office, the trip’s purpose is to recognize “the importance of the relationship between the two countries and their common bonds and shared traditions.”

Among the week’s agenda: meetings on osteoporosis and homelessness, and a visit to an organic farm.

It’s the un-Diana tour, in which a couple of middle-aged, earnest eccentrics from the English countryside take an educational holiday abroad.

They start in New York City on Tuesday, with a visit to Ground Zero and a meeting with United Nations Secretary-General Kofi Annan to discuss youth enterprise.

Next, in Washington, they’ll attend a conference on osteoporosis and a seminar on “Faith and Social Responsibility.” Charles will pick up an award for his work on preserving traditional architecture. There will be lunch and dinner at the White House, a couple of visits with school children. And they’ll mark the 60th anniversary of the end of World War II by laying a wreath at the World War II Memorial.

Then it’s on to San Francisco. There they will visit a farmers market and an organic farm in that hotbed of boomer chic, Marin County. More events with school kids. A speech on the environment and a meeting with homeless people.

And, of course, what tourist’s trip to San Francisco is complete without a visit to “Beach Blanket Babylon,” the campy, long-running musical revue beloved by generations?

The show may have special meaning for the royal pair. Its plot involves Snow White’s years-long search for a suitable prince – and her love of giant, exotic hats. Sounds a lot like the basic outline of Charles and Camilla’s decades-long, on-again, off-again romance. Not to mention the hats.

Renowned for its ever-updated topical nature, the show that Charles and Camilla will see is still being fine-tuned. But producer Jo Schuman Silver swears there won’t be any mean-spirited surprises.

“This is as big as it gets,” Schuman Silver said. “This is pretty amazing. We’re over the moon about this. It’s the Prince of Wales. … They’re a very, very attractive couple.”

See, America: Nice. You can do it.