please suggest activities in Zanzibar

we are going to spend 5 nights in zanzibar. We (one adult and a 11yo) are not swimming pool people, therefore we'd like to do/see/enjoy the local place and culture as much as possible. What activities and stuff would you suggest to do in Zanzibar? what should we not miss? i understand that Stone Town is a must, and many also seem to suggest seaside tour or diving experiences. Any insight and recommendation is highly appreciated. thanks in advance