They celebrate Thanksgiving. They do NOT celebrate most holidays because most cost money and effort (and they spend very little money or time on their children) but Thanksgiving requires no effot for them because they simply go to the mom's mom's house (my boyfriend's grandma - who, by the way, is not and has never been a JW) and she prepares all of the food... so they seem to celebrate Thanksgiving because they get a big meal at no cost to them.
My mother kind of does the same thing, though she would never be caught dead doing all of the other things on your list. Every year on Thanksgiving weekend her brothers and sister have a family "dinner", but they never call refer to it as a Thanksgiving celebration. Apparently this was a common occurence in many congregations because our CO at the time spoke out against it from the platform. He said that many JW's were visiting their family during the holidays and eased their conscience by just calling it another family get together. He suggested that we avoid visiting our families during the holidays and to arrange to associate with them at other times throughout the year.
Your boyfriend's parents sound like they are on fringe of the WTS. Though I believe such JW's are in the minority, they are probably more common that many conservative JW's are willing to admit. When I was in high school I became friends with this guy who consider himself and his family JW's. But some of the things he told me caused me to have doubts about the seriousness of his families commitment. His parents, for example, loved wild parties and loved alcohol. I think that are some JW's who are attracted to some of the doctrines of the WTS, especially the concept of living for ever in paradise, and they think that just by embracing a few of the beliefs of the WTS and by attending a meeting here or there they are in God's good graces. My brother is kind of the same way. Even though he is disfellowshipped, and even though he believes some of the things the WTS teaches is bullshit, he still believes in the whole "were living in the last days" and "JW's being saved during Armageddon" thing. I think that this belief is so powerful in the minds of some that, while they do not wish to commit themselves fully to all JW practices, they want to do just enough just in case God shows up tomorrow.