Well if you have a D3s, then don't sweat selling the D300. Get the compact you want and if that doesn't work out, get a D600 and use the same D3s lenses - maybe add a 35mm f/2 AIS (if you like that kind of stuff) and you'll have a nicely sized very capable camera/lens combo that will certainly outperform a compact, except go in your pocket.
My walkabout lens on FX(D700) is either the 35mm f/2 AIS or 35mm f/1.4 AFS. I like the 35mm FOV, see below.
My travel camera is a X100. It's superb. I used it with a LX3 to add some zoom capability, but have decided to "upgrade" the LX3 to a X10. The X100 so far takes way better images than the X10, but the X10 is quite capable and does have a 28-110 equiv zoom. That makes it a useful adjunct to the X100. I'll be sticking with the X10 for some time. I was able to get good snaps of my grandchildren racing around on their bikes and scooters so it can handle moving objects pretty well. I like the zoom range. The optical finder is good for street snaps, but you will loose some since it doesn't have any optical-finder-tunnel indication of focus, etc - just clear glass. You can broaden the AF spot sensitivity or rely on face recognition. It's really pretty slick. I have used it successfully in hyper-focal mode for snaps. Again quite useful.
IMO there isn't an everything compact (yet?!).
Roger It's still, ISO, aperture and shutter-speed, right?