We are flying down in july to tent camp and I've already have most of our stuff packed!LOL! I can't wait! There will be 5 of us so we are allowed to check 10 bags on the plane---Our tent will be(1)--Air conditioner(2)--Duffel bags all rolled together(3)--Cooler holding misc camp stuff(battery lantern,brita water bottles etc) (4)--Stroller(5) and that still leaves 5 bags to fill with clothes and other items!!!
We are using the MYW dining because we know we will be at the parks for most meals and are using the ME for transpotation to and from the airport.
As for expensive items I don't think you'll have much outside of cameras and video equipment and they'll be with you when you're not at the campsite and if you do have something I was told you can bring it to the front office to hold.
Plus a lot of ppl here have said they've never had a problem leaving stuff at their site so there shouldn't be to much of a problem!