We will be visiting France on a Rick Steves tour, arriving in Paris this May. After the tour, my spouse will return home but I will be visiting the UK, Spain, and possibly Italy. I am bringing gifts in my luggage for my family in Spain and would like to mail them from Paris to their home in Spain to avoid carrying them with me. Google Maps indicates there is a post office - La Poste - not far from our starting hotel in Paris. Through a combination of Google and looking the La Poste web site, I think I can buy a Ready to Send box - Prêt-à-Envoyer - that includes postage directly from the post office, just like we can in the States. There's even an EU version for sending packages within the EU.
Does anyone have experience doing this? It looks pretty straightforward. I'd like to carry as little as possible while traveling. I have also written the hotel as I cannot tell whether this size box is always in stock at La Poste or whether it has to be ordered in advance.
Here is the 5kg box:
Colissimo Prêt-à-Envoyer Union Européenne - Boîte de taille L - 5 kg
https://www.laposte.fr/pp/colissimo-pret-a-envoyer-union-europeenne-boite-de-taille-l-5-kg/p/18821