Congress sources said the three leaders would leave for New Delhi tomorrow evening and are expected to meet Party Vice President Rahul Gandhi and other leaders on August 4.
They said the meeting is expected to discuss issues connected with restructuring the party, which was due for a long period.
Last month, Gandhi had met more than 80 second level party leaders from Kerala and sought their opinion on party affairs in the state.
Mani was forced to resign as Finance Minister from the previous UDF government following an adverse remark by the Kerala High Court on the bar bribery scam.
KC(M) is the third largest partner in the Congress-led UDF Opposition.
Mani and his followers believe it wasChennithala, as Home Minister in the previous UDF government, who hatched a "conspiracy" in the bar bribery scandal to weaken him ahead of the assembly polls held in May this year.