These packs will be fine charged at 5 amps. The 2C charge rating doesn't make much difference on most chargers anyway. The CC/CV charge system for lipos means that it will only charge at the higher rate up until it hits 8.4 V, then the charger backs off the voltage and amps to only what the battery can drink.
In my experience it's rare for the packs to continue to charge at a full 1C once it's hit 8.4V, much less 2C. If your charger has a display you can watch the charge rate slowly drop as the pack nears full capacity. On our ICE's, it drops to around 0.1 amps by the end.