As a general rule, timeshare is not all-inclusive. In fact, most timeshare properties come complete with fully equipped kitchens and dining areas where you can prepare food for the whole family and save yourself money on eating out at every meal.
However, when you buy a timeshare that is located on a resort, usually these complexes function as a hotel too, catering for guests as well as owners. Sometimes these resorts will offer both room only and all-inclusive packages which means that timeshare owners can benefit from an all-inclusive package, if they choose.
Timeshare resorts that offer all-inclusive packages are very likely to offer owners the option to buy vouchers or a pass which might cover anything from a day to the whole time of your stay. Very rarely is this compulsory and you can often opt for a few days all-inclusive. In these cases, timeshare owners really get the best of both worlds where you can can pick and choose how all-inclusive you want your vacation to be.