Depends on what you want, kardamena is very british - loads of youngsters, teenagers, drinking etc etc. There's not much in kardamena to look at, though you can do all the usual watersports etc. There's trips out by boat to other islands, the volcano at Nisyros for instance plus trips down the coast. Kos town has more to see, ruins, castle and stuff.
As I said, it depends on what you want. If youre mid thirties you may be past the all night drinking, falling over in the street stage - or you may not be!!