Here's a sample if you were to tailor make your holiday.
Eurostar:
2 adults, 2 children =
£206
Outbound: October 17th dep: 0709 arr: 1159
Inbound: October 19th dep: 1926 arr: 2156
Both change in Lille but it's very simple to do, even with kids and luggage.
www.eurostar.com
Hotel:
2 nights Holiday Inn: £180 family room (1 double bed, 1 bunk bed)
www.ichotelsgroup.com
2 nights Kyriad: £110 (1 double bed, 2 single beds)
www.kyriad.com
Explorers: £166 Crew room (4 people)
www.explorershotels.com
Dreamcastle: £238 (includes breakfast)
www.dreamcastle-hotel.com
Disney's Hotel Cheyenne: £334 (including breakfast & PARK TICKETS! & an extra 2 hours a day in the park (extra magic hours) You can also add an extra night for another £65
www.disneylandparis.com
Tickets:
If you choose to stay at a non Disney hotel you have 2 options for tickets:
3 day hopper: 2 adults & 2 children = £324
www.disneylandparis.com
or
Fantasy Annual Passes: 2 adults & 2 Children = £350, these give you access to the park 335 days a year plus 10% off in the shops & restaurants!!!
Totals:
Exploreres: £722
Dreamcastle: £794
Holiday Inn: £736
Kyriad: £666
Disney's Hotel Cheyenne: £530
As you can see, it is cheapest to stay in the Cheyenne. Although it's not the most luxurious hotel it is far more exciting than the others. Also, because it's a Disney hotel you can have your park purchases sent directly to the room (so you don't have to carry them around the park!)
Obvoiusly these are just sample dates, you may want to stay longer or at the weekend.
If you want to save more money it often works out cheaper if you take the eurostar to Paris and then switch to the local train (RER). I would recommend it with two young children and luggage though as it involves a connection (Paris Nord - Chatelet les Halles - Disney).
Hope some of that helps!