To get the full effect of coriander, it should be crushed. For less effect, cracked might do.
I would taste as you move to secondary to see if you get the full flavor your want and possibly add some in secondary, although I don't know how well that would work either. Maybe a coriander 'tea' with it crushed and steeped would work?
I'm sick of the coriander taste anyways. Good luck and let us know how it turns out.
Also, there's another Saison thread where seefresh and I are planning a possible Saison swap. If you'd be interested, come on over.