Occupying children and grandchildren while boating calls for creativity. I find it helpful to offer a variety of activities suited to the age of the child.
A quiet time set aside each day allows everyone time to renew and refresh themselves for the balance of the day. Reading is an excellent quiet time activity as are audio books to be enjoyed individually or as a family.
A variety of audio books for all ages can be purchased and downloaded online, loaded into an MP3 player for individual use or burned onto a CD for everyone to enjoy.
I use the following site for a large selection of audio books Kids - Young and Old