redtail:

I think I would use a servo.

Sorry, couldn't resist.

Probably the easiest would be a direct link from the servo to the center flap and a bellcrank arrangement to operate the two outboard.

You could use the Du-Bro #183 ball connector to link the outer ones, this link is made to attach two pushrods to the one ball socket, with one coming out opposite the other.

Hope this helps.

Bill.