Layover at CDG - duty free shopping and shipping

You will be able to do that when leaving the Schenge zone, not when entering.

To elaborate on the above, when shopping at duty-free, you have to show your boarding pass, proving that you are heading out of the zone. Maybe shipping purchases out would qualify, but that’s a question for someone with very specific knowledge of the rules. Also, shipping costs might wipe out any savings.
Btw, you didn’t mention what products you are interested in; but I have found d-f to be mostly unattractive. The largest categories of products are tobacco, cosmetics, perfumes, and high-end alcohol. After those, there is usually an assortment of luxury apparel. None of that is of any interest to me.
An alternative to d-f is reclaiming the vat upon departure, on big purchases you make during your trip. You can search here to find out how to do that.

When you leave Europe you will have an opportunity to shop the Duty Free shops (you actually won't have a choice; you have to walk through the duty free area to reach the international departure gates). As the PP noted, it's not necessarily a bargain unless you are looking for certain cosmetics, tobacco and alcohol. With respect to cosmetics and alcohol, bear in mind that if you are changing planes in the US, the TSA 3-1-1- rules come into play. While you will carry on your items upon departure from Europe upon changing planes in the US you would have to somehow manage to pack and check any liquids, gels or aerosols.

FYI, Longchamp has all its products -10% at the Longchamp stores in the International terminals. Departure only.

We will have a three-hour layover at CDG on our way to Italy

From what I have read, three hours at CDG to transfer, may not leave you with much shopping time

My wife looks through the DF shops these days and is not impressed with the prices. It's a global economy now. As noted, perhaps better to shop while travelling and claim the VAT refund.

It was fairly breathtaking just how full of shops CDG is, I thought we were in a shopping mall. Standing in the doorway of one brand, you can look down the terminal a ways and clearly see another one of their shops.

Thanks so much…I shall do mostly window shopping there… :)

I was told by TSA that you bring duty free liquids through a US connection. After all, most duty free shops are after luggage is checked.

TSA will open it in the US and check/test it, but it is allowed.