Hi there,
There are a couple of other areas to check if this creep is excessive, but it is normal as has been said earlier.
If the load compensator valve above the rear axle is seized (If fitted to US versions - is present on UK version) Problems here amplifies the poor pedal feel, as does worn or seized brake caliper slides on the rear.
Observe the rear calipers from under the vehicle with a good light and get an assistant to press the brake hard while you watch, if the assembly appears to bend or tilt over when pressure is applied, there is a good chance you have an issue with the slides. Once this is sorted and/or the compensator (if fitted) is free and easy you will be assured of the best 'pedal feel' you are going to get.
If you think you have a sinking pedal now, just wait until you start to 'bed in' a new set of front pads on old rotors !!
Time to worry is when the pedal sinks with the engine not running (press pedal a couple of times to discharge the huge capacity vac servo) once this is done you should have a rock solid pedal that does not decend at all. If the pedal creeps under these conditions, then its likely your master seals are passing and need to be attended to.
Rare and not often the case is air trapped in the ABS block (possibly after major pipe replacement etc) this can be fun and usually the best way is several gravity bleeds at each of the outputs of the ABS block. A final pressure bleed usually finishes the job.
Hope that helps
All the best
Steve