Step one is to determine how much power all of your devices need (amps) times how long you expect to run them (hours) to get the minimum amp hour requirement, multiply by a fudge factor to allow the battery to age and then you can start to look for specific batteries.
Lithium gives you the best poop per pound ratio. The Lithium Iron Phosphate is supposed to be the most stable of the chemistries. But, since you will not be charging the battery in the airplane, the risk is significantly reduced. Put a fuse right at the battery to prevent a short circuit from causing problems.
Where do your portable electronics live? Bouncing around loose or nailed to the panel? How many devices do you want to plug in at one time? How big a wire tangle are you willing to deal with?
I suspect that you would want to connect a multi-outlet extension cord directly to the battery (with a fuse right at the battery) that you can run to where it is convenient to connect your stuff. I further assume that the various devices have the cigarette lighter style connector. If so, the first thing to do would be to cut those off (they are designed for lighting cigarettes, not aux power connections) and replace them with some sort of polarized plug from the radio control airplane world. Much less bulk, much more reliable connections. Or, you could put the battery and all of the devices into one box that is strapped to the floor, or...
