We bought the 10-year old a Hermione wand back in 2012, but we got it from the street cart at the exit from Hogwart's rather than from inside Ollivander's. We still stood in line to see the "show" though (one of the longest lines all week, I might add), and even though our daughter didn't get picked, we enjoyed it very much. Later, near closing, when the line wasn't as long (and when there weren't any other youngsters in it so she stood a very good chance of being chosen), she wanted us to try again, but then it started to rain, so we took off and missed our chance. She might never forgive me for that.
I think that Gregoravitch's could just be a store, without the "wand chooses you" production. I think it would be great to have a place there to buy wands and things without having to get in line and see the show if you don't want to be a part of that. So maybe Gregoravitch's will fit that bill for people who just want a quick retail transaction but Ollivander's will be for those that want to see the "wand picks you" experience.