Nope its all good. The balance port on the charger can do it. You don't need any external extensions or boards. If you do wanna go that route, you would need a balance board or extension that is JST XH, 2 to 4s. But you can just put the balance plug directly into the charger and it will be good...
Any ordinary modern RC LiPo charger will work. Just need correct charge and balance leads for your batteries. Me as a racer, a charger for me is more like it has to charge more than 10A x 2 (dual charger) at the same time.
When looking at a charger, my options are needed, IR reader/meter...