We are from Vancouver Island, will be travelling with my parents, my DH and two daughters (ages 8 and 5 at the time). I have been 4 times, however the last time I went was 19 years ago in 2007, for my high school graduation present! This will be the first time for my husband and our daughters

We are planning on being away for a week, I'm thinking from October 22-29.
OOH!!! EXCITING!!!!!
Transportation
With our dollar being so .. well.. ugly.. you might consider a little road trip that will eat some time away from your actual trip. If money is not really an issue, then I would start looking into flights and a car rental. To start, I would just google YVR to SNA and SEA to SNA. Weigh your options between where to fly from and doing a road trip.
Tickets
Rumour has it that they may increase the price (again) this month (Feb), but you can definitely find the cheaper tickets at sites like undercovertourist.com
Stay
With your daughters at 5 and 8, you can opt to stay offsite for sure (which is going to be a LOT cheaper) BUT you do lose on some of the Disney magic you get from staying on site. There's really not too many onsite properties compared to Disneyworld so have a quick glance what the resorts on the official disney website and see if you want to fork down the money for onsite.
Otherwise, you can start looking into offsite properties, which also happens to be listed on the disney website
Food
There are tons of restaurant outside of Disney you could go to but I would do at least one dinner inside because it's just MAGICAL!!!!
Itinerary
It'll also be a good time to start figuring out what you want to do per day. Try not to cram too much into a day because by the last couple of days, you'll be all burnt out. Your DDs are definitely old enough to forgo naps but in case you need to wind down a bit, don't hesitate to go back to the hotel and go to the pool or something like that.
When planning, also take into consideration if you and your family would prioritize character meets? doing all the riders? or any other goals you would to accomplish.
There's a special Halloween special that happens during your visit, but I don't think anything is released yet. I'm not sure if Disneyland works the same way as Disneyworld, but in Disneyworld you can start entering at around 4pm (which means you don't really need to pay for an extra day ticket for disney).
Conclusion

HAVE FUN!!!!

and we are here to help!