From your photo, just lowering the soil isn't going to keep the run off from crossing the sidewalk, too much of an elevation change up to the trees. Water is going to run down hill, gather up at the sidewalk till it overflows and still do the same thing. You need some drainage ditches to direct the runoff to a spot where you can install a drain UNDER the sidewalk for the water to get off the lawn.
Raising the sidewalks by 4" would take about 22 yards of concrete (1800 sq feet of surface)but still might be cheaper than your planned removal of 4" of soil and re-sodding of the area which would be very labor intensive and still not solve your water overflow problem. The concrete elevation change would be at most a 2 day effort.