When he received the offer of an all-expenses-paid trip to the Canary Islands, the Rev. Raymond P. Jennions decided not to knock opportunity.

So yesterday, Jennings, pastor of National Baptist Memorial Church here, boarded a jet to join 150 other ministers, theologians and professors at a week-long "ecumenical conference" at a Tenerife hotel -- courtesy of the Rev. Sun Myung Moon's Unification Church.

The conference, "Exploring Unification Theology," may cost the Unification Church as much as $600,000 and is one of a series of 35 such all-expenses-paid gatherings organized over the last two years by the New Ecumenical Research Association (NEW ERA), a group associated with the Unification Theological Seminary in Barrytown, N.Y., said Richard Quebedeaux, a senior consultant to NEW ERA.

Quebedeaux said the conferences, which he estimated cost the Unification Church "several millions of dollars a year," are designed to provide an ecumenical forum for theological discussions and to counter what he called "so much negative publicity" and "the uniform nastiness" of press coverage of the controversial church.

Jennings, acknowledging that some of his friends told him he "was crazy to go," said he expects the conference to be "a sincere theological exchange," an opinion echoed by others, like Frederick Ferre, head of the philosophy department at the University of Georgia-Athens, who accepted invitations.

Critics of the church, however, said they viewed the conference as part of the church's increasing public relations efforts to gain legitimacy by associating itself with members of the religious an intellectual establishment. a

"The Moonies are investing millions and millions just justifying their existence. They're trying to say, 'We're just like all the other religious groups,'" said Steve Hassan, president of Ex-Moon Inc., an organization of about 375 ex-Moonies.

Jean Merritt, a pyschiatric social worker and an outspoken opponent of the Moon church, said such seminars are "staged" to allow "the Unification big shots to have their pictures taken with these people."

In the past, some professors have gone to similar gatherings sponsored by "front groups," not realizing that they were financed by the Unification Church, and have withdrawn when they found out they were sponsored by Moon, she said.

Often invitations are sent in a sort of "shotgun" spray to lists of professors and well-known intellectuals, and even if only a small percentage of them accept, there are professors and well-known intellectuals, and even if only a small percentage of them accept, there are enough to form a conference, Hassan said. Some are recommended by others who attended previous conferences, he said.

Other Moon-funded organizations regularly hold seminars for "special interest groups" such as lawyers or scientists, including Nobel laureates, Hassan said. Earlier this summer a Unification Church conference in Israel was canceled after protests from the American Jewish Congress and the American Jewish Committee.

About 30 Unification Church members at the Tenerife conference, most of them graduate students at American universities, will lecture on topics such as "the principle of creation" and "the fall of man." An optional movie called "Reverand Moon, the Man and the Movement" is also scheduled.

Some guests were asked to write responses to Unification literature mailed to them before the conference, and nearly all the papers are critical, even scathing, Ferre said.

Moon's followers are criticized up and down in these papers," said Ferre, who said he was attending the conference as "an intellectual missionary."

"They asked for it, and they're paying for it and they're going to get it," he said.

NEW ERA executive director John T. ymaniatis, reached by telephone in Tenerife, said the "contrary to media opinion, we're not afraid of having our theology criticized," and refused to talk further with a reporter.

A list of the 35 major NEW ERA conerences in the last two years ranges from "Critiques of Marxism and the Search for New Principles," and "Islam Nification Dialogue" in Barrytown, to "Advanced Seminar on the Principle of Creation" in San Juan, Puerto Rico.

Some are held in intriguing places such as the Canary Islands and the Bahamas, "in part because that is what it takes to get people to get there," Quebedeaux said.

He noted that some criticize the fact that the Unification Church spends so much money on such events. "But then," he said, "the question is, 'How much money does [Moral Majority leader] Jerry Falwell spend?' Do they ever ask that?"

Quebedeaux, who has written books about the evangelical movement, said he became involved with such conferences when he helped organize a "dialogue" between evangelicals and Unificationists in 1978.

In March 1980, after organizing several such everts, he helped form NEW ERA, which now has a 21-member advisory board. "We realized we had to have an organization to coordinate these things," he said. NEW ERA is affiliated with the Unification Seminary and financed by the Unification Church, he said.

Quebedeaux, who described himself as a "theological broker," said he receives a $1,500-a-month retainer as a consultant for NEW ERA, and gets $500 plus expenses for attending twice-a-year meetings in New York.

He said he is a "born-again Christian, a Congregationalist," and disagrees with Moon's theology, but helps with the conferences in the interest of "ecumenism."

And some of the guests say they're going in the interest of teaching and being taught.

I've been kind of fascinated with their movement," Jennings said. "I was a pastor in Berkeley for seven years when they were just getting started out there. But I've never learned much about their theology."

Jennings, hwo left his pastorate this week to write for a Baptist newspaper, said he hopes to tape-record some interviews at the conference for news articles.

A Washington physician also going to the conference said he attended another about two years ago in the Virgin Islands, along with about 200 doctors and professors.

The physician who said he is from Africa, declined to be mentioned by name. He said he hopes "to change opinions" at the conference and "expose the ridiculousness of the Moon argument and God. The concept of God is irrelevant to modern times," he said.

Ferre, who became a Methodist two weeks ago, acknowledged that part of the conference's attraction is the fact that "they keep picking these interesting places to go." He estimated his airfare and hotel fees would probably cost the Unification Church $1,300.

He attended another such conference for college professors in Hawaii three years ago, and was probably invited then because he published several books on philosophy and religion, he said. Another professor in his department also accepted an invitation to the Canary Islands conference, he said.