I've sold all my 50mm lenses, my 35mmL, and my 85mm f.1,9. They were great lenses, but with the high ISO capability of the 5D MK III, my 24-70 MK II and 70-200mm MK II and 100-400mm L along with my 16-35mm f/2.8 get almost all the use.
I kept a few primes, 15mm FE, 17mm Tokina f/2.5, 100mmL, and I just could not part with my 135mmL.
Do what works for you, you are young enough to get them later. Your new baby should come first.