Is the KWV11-C card the best option for that or are
there other options? I
have looked
around a bit and have seen some other RTC boards but don't know if they
would work.
There are third-party options that are KW11 compatible and generally have more features.
They're also usually nearly free when you find them! Beware of battery damage, many
had a NiCd cell or pack mounted on the PCB.
Thanks,
Jonathan