If you do decide to naturally carb it, remember that you'll need less sugar for the keg portion than for the bottle portion. I think I've seen the number 50% normal priming sugar thrown around, but not sure how accurate that is. It has something to do with the differences in head-space and surface area between one keg and all those bottles. So you'll have to add the smaller portion to the whole batch, transfer half to the keg, then add the rest of the portion to the bottled batch to get them to come out the same carb level. Not saying not to naturally carb, just warning you so your keg doesn't overcarb or bottles undercarb.
Also, naturally carbing will give you slightly more sediment than force carbing, but in both cases after the beer is carbed and cooled you'll want to pull a pint or so off first and toss it, since most of the sediment comes out in that pint. After that, so long as you aren't jostling the keg around, it should pour clear.
On the other hand, if you decide to force carb the keg, you can't go wrong with setting at serving pressure and letting it sit. Use this chart to figure out how carbed you want it to be and set your pressure depending on the kegerator temp. Hook the keg up and let it sit cold for 2-3 weeks, and it will be ready to go. That extra time also makes sure everything settles to the bottom of the keg, and gives it a chance to cold-age for a bit before serving.