My son's bike currently has 53/39:28/13 gearing and is hard for him on climbs, I ordered a compact 50/34 crankset in oder to ease the gearing up front.

Now the question is, should I change the cassette with a different gear combination? or should I keep the current one. I have 2 spare road cassettes that could use if needed, 23:13 and 26:12.