I love sewing and making tznius clothes for myself, family, and friends. It is not a business; it is an activity I engage in for fun and to ensure I am comfortable while tznius. Although I have been sewing for years, I want to attend Costume College which is a convention for dressmakers and costumers. Many of my sewing friends have reported excellent results on their work by attending the speaker’s presentations which take place during the day on Friday, Saturday, and Sunday. I’ve verified with the hotel that if I stay inside the hotel and reserve a room on the first or second floor, that I will not encounter a situation that requires I walk through electronic doors or elevators. Their rooms have a key option or the staff would be happy to let me in. My shaila is, would it be possible to attend the presentations on Shabbos as long as I did not engage in note taking or any hands on projects during Shabbos?
In order to keep the sanctity of shabbos, one of the things we are not allowed to do is to occupy ourselves with our personal business that involves melacha, even if we are not actually doing it. For example a person may not go to his field to check what repairs it needs, (plowing etc.). The same would apply to going a building site to examine what has to be done r to buy it. This convention is all about sewing, which is one of the melachos prohibited on shabbos, therefore we do not involve ourselves with it on shabbos. Aside from this, the whole atmosphere in the hotel puts you in a very “un-shabbosdik” atmosphere, and takes away from the sanctity of shabbos. We are taught that one does not lose out from keeping shabbos, and I am sure that H-shem will pay you back, and arrange things so that you will not lose out by not going.
Shulchan Aruch O:CH 306-1, PiskeiTeshuvos 306-2.