Seesawing hopes of averting civil war here lifted slightly today with the news that three key players in the Lebanese drama were gathering in Paris this weekend.

Robert C. McFarlane, President Reagan's special Middle East envoy, is to meet Moslem Druze leader Walid Jumblatt, who has threatened an all-out assault against the frail Lebanese government if his demands for a larger political role here are not met. Also flying to Paris today was Wadi Haddad, national security adviser to President Amin Gemayel.

The Christian Phalangist Voice of Lebanon radio station asserted, "Features of a political settlement in Lebanon are taking shape in France."

However, the situation here remained perilous and confused. Citizens continued to line up outside the American Embassy to get visas, and the airport is so clogged with those fleeing that travelers are now advised to show up three hours before flight time.

Jumblatt sent an appeal yesterday to Druze in the Chouf Mountains overlooking Beirut, telling them that "the hour of challenge is approaching." He referred to the planned Israeli pullback from the region and Gemayel's planned deployment of the Lebanese Army there. Jumblatt urged followers to "stand fast and resist" the Lebanese Army deployment "in defense of their honor and dignity."

Other Syrian-backed government opposition leaders allied with Jumblatt in a National Salvation Front warned in a statement today that it would be a "national disaster" for Gemayel to move troops into the Chouf without reconciliation. They proposed a meeting with the president in Tunis or in Syrian-controlled northern Lebanon.

Gemayel, on state television last night, pleaded for public support for the Army's deployment. But he signaled that he had no intention of submitting to Jumblatt's demands for revising political arrangements to give Druze more power before the deployment.

Gemayel and Jumblatt are both scions of leading political families with a long tradition of mutual antipathy. One problem in resolving their current differences has been simply getting them in the same room together. Gemayel has insisted that the Druze leader meet him at the presidential palace. Jumblatt has demanded that any talks be held at his family's feudal palace in the Chouf.

The French newspaper Le Monde reported today that Gemayel is now prepared to meet Jumblatt on neutral ground.