Hi...don't worry....you are talking about 2011....

....well, that's around the time we would like to go to the USA and take our girls ( now almost 5 and almost 7) to WDW...so I exactly know how you feel.
Why don't you start buy readinf the BRit's Guide to
Disneyland Paris Resort,by Simon and Susan Veness. It's an excellent book.
I already bought the one for Olrando and WDW. Of course things will change from know until 2011, but it will help you get an idea and start planning.
I think one of the best part of all is planning....and even saving is not so difficult because it's something we all really want to do...so we don't spend so much on "junk" instead save it for the trip !
You could also start by saving some $$ in a jar, and then exchange them to Euros...unfortunately the exchange rate is not good for you , so everything will be a bit more expensive, so that's why you shoulr start saving know.
Also...why son't you order a summer catalogue from DLP...that will help you get an idea in prices...of course they will change, but at least you can get a general idea.
Hope this helps....and have fun.