We took the nature trail that circled the vistor center, which took about an hour to finish. I feel as though anyone is capable of completing the trail regardless any previous hiking experience. Three of us ventured in to the tunnel cave; I recommend bringing a flashlight to get everyone to go.
Rent the canoes from the front office. We rented for half a day because we got a late start, but a whole day is a much better deal. You have to go upstream first, which can get tiring if your going with someone that has never canoed before :-).