Ok, I understand why they are recommending the high fat milk. They don't want the BG spike, and the fat helps slow down the carb absorption.
But my thinking has been that I didn't want slow carbs, I want fast carbs so I can more efficiently restore muscle glycogen.
I mix milk, whey protein, and chocolate milk powder mix (like Ovaltine or Nesquik, which is basically just pure sugar!). Something like that would usually spike me very high, so I counter that with a fairly big dose of insulin. The larger-than-needed insulin dose prevents the spike, but I also have to keep a close eye on it, and then take in more simple carbs an hour later.
So there is a bit of a risk in the trade-off. I don't mind the risk of a low BG later on, because it's just an opportunity to eat or drink more! But of course, with a child you want to be more careful.
What I am doing is possibly not ideal for your situation. I have been trying to follow non-diabetic recommendations, because I didn't want the diabetic "safety" advice to get in the way of the "performance" advice.
Since you are kind of just starting out, go slow and careful. Make small adjustments over time. A good healthy meal a few hours after practice will also replenish the glycogen, it will just take a bit longer.
A lot of the stuff we are talking about here, including the high fat milk after workouts that you referenced, is in the Colberg book. I just found it in chapter 4. In that chapter, she also references the optimal time to restore muscle glycogen is immediately after a workout, and the 24-48 hour time it takes to restore. That's a good chapter to review.