You can pick and choose. Note that on the second day all three climbs radiate from the same point. Well one of the climbs, the first one to glacier lodge is about a mile up the road. On the first day the climbs are pretty far apart.

Also as a tourist you would want to keep in mind that the last climb of each day has real food at the end and the other two just have bars/gels/etc. So if you were going to do one climb each day you would want to do south lake on the first day and of course white mountains on the second. Those two climbs alone account for nearly half of the total elevation.