I've been told wheat is fine as a part of the feed. A caution is that if it is not dried properly, it can get moldy, and moldy feed is bad news.
I have added a small handful of dry hard winter wheat to my ducks' feed pellets from time to time. I have also given them sprouted wheat, and wheat greens (just let the sprouted wheat grow a few inches and green up). Wheat has some nice protein in it. It's a grass. Another caution is not to give them too much "seedy" feed. I forget what problem that could cause. Nettie or Duck_feeder may be able to enlighten us on that.
So, I would consider getting some to add to their feed occasionally, but would keep it in a dry, tight container somewhere cool.
By the way, I also add rolled oats to their feed. I started doing so to cut protein percentage, but have kept it up to give them something a little different, with some nice fiber in it.