The wine in the sorbet helps keep it from freezing too hard. If you want to omit it, you'll probably need to take the sorbet out of the freezer several minutes in advance before scooping.
I tried it with both amounts of sugar (sugar also helps keep things from freezing too hard) and preferred the flavor with 3/4 cup, although you're welcome to use either. For more information, check out my post,
Tips for Making Homemade Ice Cream Softer
I've not used dried elderflowers (which I just learned about), but if you try it with them, let us know how it turns out in the comments.