Error Near Exec Statement

Hi Guys, I have been trying to get this SQL string below to run, but for some reason I carry on getting an error near the EXEC Statements.

Does anyone have any idea what I doing wrong?

CREATE PROCEDURE [dbo].[UpdateWarnings]
@EndDate DateTime
AS
DECLARE @iid varchar(100)
DECLARE @fid varchar(100)

SET @iid = EXEC('SELECT id FROM memorial WHERE warnings >= 3 AND expires <= getdate()')

IF @iid <> ''
BEGIN
EXEC('UPDATE memorial SET active=0 WHERE id IN ('+ @iid +')')
END

SET @fid = EXEC('SELECT id FROM memorial WHERE warnings < 3 AND expires <= getdate()')

IF @fid <> ''
BEGIN
EXEC('UPDATE memorial SET warning=(warning+1) WHERE id IN ('+ @fid + ')')
END

IF @enddate <> ''
BEGIN
UPDATE warnings SET startdate=getdate(), enddate=@enddate, warnings=(warnings + 1) WHERE id=1
END
GO