How long will the trip be in total? If you DO decide to stop in LA either on the way TO Orlando or on the way back home to Australia, you could do 2 or 3 days at
Disneyland for a fun comparison. If you opt to do that, save money on your lodging and stay at one of the hotels along Harbor Blvd. Best Western Park Place Inn is <5 min walk to the Disneyland & California Adventure main entrances and they include free breakfast.
Then you can fly on Southwest Airlines from either LAX, the Santa Ana airport, or Long Beach airport to Orlando (and Southwest doesn't charge for luggage up to 2 bags per ticketed passenger).
Re: OKW - I haven't stayed there, but I've heard that the bus service at that resort can be frustrating.
What time of year is your trip?
Re: travel together or travel separately - there's no right or wrong answer here. The parents of the 8 children might find it helpful to have you travel with them so they have an extra 2 sets of hands to help them on the long trip over there.
When you arrive at your destination, everybody will have jet lag for a couple of days. So plan on taking it easy for those first couple of days. It might take the toddlers/preschoolers a few days to adjust to the new time zone.
Whenever we've gone on a Disney trip, the rule for our immediate family is everybody gets to pick one "must do thing" for the trip. For example, for YDD, it's usually "I want to ride Splash Mountain or Fast Choo Choo" (aka BTMRR). For DH, it's "I want to ride Pirates of the Caribbean." Try to do those "must do" things early in the trip.
And then the attitude/mindset that we all have is that once your "must do" thing is achieved, then EVERYTHING ELSE is icing on the cake.
If somebody in your group thinks that everyone HAS to spend every waking moment with everyone else, then you all are going to have a totally miserable time. You should EXPECT that everyone will need some down time from everybody else regularly during the trip.
You should also expect that at some point, sometimes frequently, ALL of the children will have moments where they are grumpy, cranky, ornery, and not fun to be around.
You might also expect that the grandparents might not have as much energy as the kids & parents do.
1 family might be a "up at the crack of dawn" crowd while the others are a sleep-in family. TALK about this ahead of time amongst all of the adults. Figure out how you'll handle that.
I think that you should advise the parents to plan on a max of 2 days in a row of park days, followed by 1 rest day. If you can afford it and if it's operational when you go, on one of those rest days, have dinner at the Hoop Dee Do Revue at Fort Wilderness.
Come up with a game plan with the parents for handling little ones who can't ride the thrill rides yet while also accommodating the older kids who want to do roller coasters all afternoon.
Decide whether you all want to go into the same park together each day or if you'll do something like alternate (i.e., 1 day at a park together, the next day everybody does their own thing). After a few days spending so much time together, you will all start to wear on each others' nerves. For example:
- arrival & day after arrival in US - no parks. Rest, go to pool.
- day 3 - 1st day at a park. Plan on ONE meal together. Maybe everybody goes on ONE or TWO rides together. Take a big family photo in front of the castle. Then you split up.
- day 4 - Epcot, for example. Good options for stuff to do together would be Spaceship Earth, Living with the Land, Frozen Ever After (pretty sure you can take toddlers on these sorts of attractions). Take big family photo somewhere. Eat a meal together (Sunshine Seasons, for example, for QS to save on $$). Then split up.
- Day 5 - day off, no parks today. Good day to plan some other activities for kids of various ages. For example, there's archery lessons at Fort Wilderness. Or horseback riding. Or rent a canoe or kayak. Or rent a boat for an hour. Fill in with pool time + movie night outside (most of the resorts have this).
- Lather, rinse, repeat.
Make a plan with the parents so each set of parents gets 1 date night, if possible, without children. That'll make their day, heck it'll make their year.
Speaking on getting on each others' nerves, all of the adults, if possible, need their own bedrooms so that you don't have to listen to them snoring and vice versa. You're not used to having roommates like that day in, day out and neither are they. You'll all have a better time together on the trip if you can manage the sleeping accommodations like that.
