We have cruised in prior years over Thanksgiving on HAL ships and are again this year.
The menu will offer all of the traditional dishes most of us are used to. Turkey with all the fixings and a selection of pies etc for dessert. It is wonderful....and best of all, they do the shopping, set the table, do the cooking and serving and clean up the whole mess after we've eaten.
We cruised over Christmas and New Years last year and it was also great but a Thanksgiving Cruise is pretty great IMO