You can't PEAK charge cells in parallel. That's why you don't normally see NiCd or NiMH cells used in parallel.

The constant current, constant voltage used on Lithiums works fine on cells in parallel. In fact you are much better off to charge two cells in parallel than series.

You have to charge LiPo cells to 4.2V each. If they are in parallel and the charger goes to 4.2V, then both cells must be at 4.2V. If the cells are in series then the charger will need to go to 8.4V. One cell could be 4.1V and the other 4.3V.