A group of conservative political activists met yesterday to map strategy for the scheduled April 15 vote in the House on aid to the Nicaraguan rebels, including a tentative plan to target for defeat a handful of lawmakers who oppose the $100 million aid package.

David Keene, chairman of the American Conservative Union and spokesman for the coalition of about 30 conservative groups, said letters emphasizing the importance conservatives attach to aiding the counterrevolutionaries, known as contras, will be sent to more than 50 lawmakers who are considered swing votes on the issue or who face tough primary or general election contests this year.

He said the group made a tactical decision to wait until after the April 15 House vote before deciding "on who we are going after in the sense of retribution" in their reelection campaigns.

But Keene named seven lawmakers -- three Republicans and four Democrats -- he said will likely be on any list of conservative targets growing out of the contra aid dispute.

He said they are Reps. James Ross Lightfoot (R-Iowa), Sherwood L. Boehlert (R-N.Y.), John G. Rowland (R-Conn.), J.J. (Jake) Pickle (D-Tex.), Melvin Price (D-Ill.), Marilyn Lloyd (D-Tenn.) and Howard E. Wolpe (D-Mich.).

These legislators opposed aid to the contras when the House, by a vote of 222 to 210, rejected the Reagan administration's $100 million package last month.

The House Democratic leadership pledged to schedule a second vote on the aid package for April 15 as part of a successful strategy to hold a number of wavering moderate and conservative Democrats in line against the proposal in the first showdown vote. The Senate narrowly approved its version of the aid package last week, and a compromise plan is widely expected to clear the House this month.

Keene said letters urging support for contra aid will go to the 16 House Republicans who voted against the administration in March and to some lawmakers who have been criticized in their districts for voting for aid.

Regardless of the outcome of the April 15 vote, Keene said, conservatives will continue to view aid to the contras as a litmus test for members of Congress.