Yup, that kit will do the trick. Lake Country makes most of the pads out there, so those are likely the same pads you would get anywhere else.
Getting the 5" backing plate is a good idea only because it will fit the smaller pads if you are working on headlights and areas like that. You really don't have to worry much about scratching if you get the 6" pad though. Your pads will actually last longer if the backing plate is full size. I have a smaller backing plate when I'm working on headlights, otherwise I use a 6" pad and backing plate. In fact, that backing plate on coastal tool is the same one I use. It is flexible and really much better than the other ones I have. I only wish the FLEX 3401 had some sort of thing like that, but it wouldn't be very practical with the design of that machine. My PC7424 and my FLEX PE14-2-150 both use the flexible backing plate like that though.