DLP runs promotions all year long for every time of the year. And most european countries have their own website with different offers. For example at the same time one could have 40% discount with children up to 7 year go free, another might have 30% off with children up to 12 free, another 20% discount but half board included, another 2 free nights if you pay for 2. It really comes down to which offer is the most convenient for you. Anyone can book using any of the available offers, regardless of the country they live in (also people from the US).
Start with disneylandparis.co.uk and disneylandparis.ie which are in English. Once you get familiar with the process to get a quote you can easily navigate all the others websites with no problems and maybe the help of Google translate. Usually the american website is one of the most expensive, so it really pays off to shop around.
All packages bought on the EU websites include tickets for lenght of stay, so it makes the value of points in your example even worst, because 550€ include tickets, booking with points you have to buy tickets on top of that.
When you're ready to book, call the usual WDW call center and ask to be redirected to the Disneyland Paris call center. Just remember to account for the different timezone, so call in the morning, if you call in the evening the DLP call center will be closed. Ask to book with the offer of a specific country. You can do it also online. Nothing is shipped to your home address, they only send an email.
Probably currently there are no promotions for September 2020, start looking one year in advance, best offers come out nearer the time. DLP hotels rarely sells out and one or two months in advance they often have 50% off promotions to sell remaining rooms, so no need to hurry up. September is slow season in DLP as well.
