I've never used a planer in my bow work, which includes grinding lams. In the end, lams should have a roughened surface prepped for gluing. A lam 'grinder' of some sort is better-suited, IMO since a planer leaves a glass smooth surface... more importantly, a sander grinds a level surface over irregular grain, knots, and growth ring orientation... where a planer would invariably tear pieces out... unacceptable.
I resaw the lams on the bandsaw, then go right to the thickness sander... done in no time at all.