...
- ferry to George's Island, with picnic: http://www.yelp.com/biz/boston-harbor-islands-ferry-boston
- Aquarium: http://www.neaq.org/
- cruise in Boston Harbor
...
- sailing lessons on the Charles: http://www.community-boating.org/
- rent kayaks: http://www.paddleboston.com/boston/rates.php
...