Hi,
Generally, the best deals are with Disney, when they have a special offer on. Offers are not always the same, but the best one is 40% off hotel tickets and transport with kids under 7 or 12 stay and play free. This ended a short while ago, and may not be offered until later, if at all this year. It all depends on how their bookings are going.
The current offer is 20% off hotel, tickets and transport, with kids under 12 stay and play free.
When comparing prices, make sure you check whether park tickets are included, as this makes a difference.
There are cheaper options than staying in a Disney hotel or in resort if you are on a tight budget, and cheaper places to buy park tickets than on the Disney website.
People can help on the Trip Advisor MLV forum, which mainly covers Disneyland.They can answer most questions about resort and area.
www.tripadvisor.co.uk/ShowForum-g226865-i2224-Marne_la_Vallee_Seine_et_Marne_Ile_de_France.html
May be worth checking this site, as they seem to be offering 40% off.
www.disneylandparisdirect.com/
Also worth checking Eurostar site package prices if you are planning to travel to Disneyland by train.
Somtimes I book through my local Co-Op travel agent, as they phone Disney for the current price, then knock off another 5% for me. They need business, so always worth being cheeky and asking.