Well, you start with the children, as they're the most active and therefore have the most nutrients. Not sure how many children are around here, or how active they would be, so that's ruled out.
You avoid the sickly. That goes without saying.
The best choice would probably be the larger set of us. If you remove the excess fat and only eat the muscle, it should work. I hear fat makes good fuel for fire, though I've never tested this.
I think I'd eat all of you before everything was said and done. Probably within the first couple of days, regardless of whether or not the island has any useable resources. Sort of an overreaction. I'd regret it afterward, of course. Some more than others.
There might be a few that I'd leave alone, though... for a while, at least.