They look like nice enough hardpacks. Nothing wrong with using them in series either.
Charging is made easy thanks to my spiffy diagram I did for someone recently with a similar type of lipo pack:
Only difference really being that you could/should out a 2s jst-xh male balancer plug on the balance wires, then you can plug that directly into your charger- assuming its one with a built in balancer (or has an adaptor for jst-xh plugs, the type used on hobbycity lipos). No worries about charging them seperately, so long as you use them together as a pair and balance-charge them everytime, they will stay 'intune' with eachother as such.