Switching A Li-Ion Battery with a Mosfet
Put a search in DigiKey and filter to see ICs specifically for 3S cell configurations. You can further refine your search for the pack voltage and battery chemistry you are desiring. Then you can do another search for Battery Balancing ICs and again specify for 3 cells.

It wouldn't be prudent to charge them in parallel because it would require more current and the batteries may be at different SoCs (see my newbie question here for more info).