Your purpose is to attend xyz conference. That's literally all you have to say. I can assure you "what are you going to be doing between the hours of 6pm to 8pm on Tuesday when you have a break, and will you be commiting any code at that time?" is not going to come up.
Sure. Mentioning anything more than that will lead to trouble. But many people are not aware of how thin the line is and mention they are also going to work remote for a few hours. Or meet with colleagues for a hacking session. That's already too much.
