I currently have a trip to Maui planned for the first week in Oct. and my wife told me it would be a great reason to go out and buy a 5dmk3 (Yeah I was shocked too). My issue is that I lack lens to really take advantage of the 5dmk3 if I pick it up.
Have the following lenses
100 macro (non-usm)
With the idea to fill out the gaps in my kit, I had gone ahead and pre-ordered the 24-70mk2 back in March. Recently, I heard of 5dmk3 24-70mk2 kits on pre-order in Australia and thought that if there is a kit, I might as well get the kit to save a few hundred dollars. With the idea of picking them both up this week and then having 2.5 months to play with the lens and the camera to get a feel for when I go to Hawaii. However, now that the 24-70 has been delayed to the end of Sept. I am concerned that the lens won't arrive in time before i leave, and even if it did and i got the kit, it would only give me a week or two to play with the camera and get used to it.
Now, if there isn't going to be a kit, then I would just go ahead and pick up the 5dmk3 now (or wait at least until after the announcement coming later this month). Though be gimped with my lenses as I really prefer shooting on my 10-22mm. So far this year, this lens accounts for over a 1/3 of all my pictures.
What do you need in FF? A 7D would be good for your trip if you already have the lenses to go with it.