For us, its' completely voluntary and the kids are responsible for transportation and hotel if they go (we are on the NW side of Houston, so it's only about a three hour drive).
They meet me Friday morning, get registered, and we head to the exhibit hall. Knowing they will spend a lot of time there, I ask that they attend at least three workshop sessions. Between the three sessions, lunch, and the exhibit hall, that takes us up to College Night. The parents pick them back up and accompany them to CN - at that point I'm on my own. (Sometimes the parents stay all day and sometimes they go do their own thing in SA).
The kids are there Saturday, usually, and will attend a morning workshop or the exhibit hall and then take in the All-State band for our classification. Their parents have always accompanied them on Saturdays.
Both the adults and kiddos have been happy with this arrangement. We do apply and receive the travel grant from TMEA every year.