Will we be hassled by local people?

Tanzania/Zanzibar is not as bad as some destinations like parts of Egypt, the Gambia, parts of India and Goa. There are, of course, some local lads who will approach people asking if they want tours or transport organised, etc. or offering visitors goods, sometimes of dubious legality! A reasonably assertive, but not aggressive, “No, thank you” will usually be sufficient.