Yes. God has free will with respect to what He does not necessarily will because God necessarily wills His own goodness, but other things not necessarily (Q19 A3).
It is manifestly impossible for Him to will the evil of sin; yet He can make choice of one of two opposites, inasmuch as He can will a thing to be, or not to be.
In the same way we ourselves, without sin, can will to sit down, and not will to sit down.