Note that there is no difference between coherent and incoherent light, expect for the bandwidth (the range of frequencies in the light). Coherent and incoherent light sources can always be exchanged in any interferometric experiment, the only difference being that with an incoherent light source the interference fringes become less visible if there is a difference in the path lengths in the interferometer. With a coherent light source there can be a large difference in the path length, and fringes will still be seen. This means it is easier to set up experiments using coherent sources, as you do not need to worry about getting the path lengths exactly the same (anyone who has worked in an optical lab will know about this!). I fail to see how using coherent light makes any difference as to whether you can use point sources or not.