Possible agenda based on my experience with AA conferences:
Fri eve 7pm-9pm Opening meeting but not the 'hottest' speaker
Sat mornings and afternoons - workshops or smaller groups with meetings geared to specific topics
This could include a mens meeting and a womens meeting as the issues differ between the sexes.
Sat eve 7-9pm Big meeting Big speaker or speakers
Sunday morning (In AA it's considered "spiritual" meeting often with an athiest presenting )
Go no later than noon so people can get flights home in the afternoon.
This schedule allows for 3 to 6 big speakers in the main auditorium.
Dallas sounds good as a U town and an airline hub city
Advanced registration will help get advanced money to help with any fees including speaker fees or if the speaker is volunteering time, paying for their airfare and hotel.
A closeby-hotel hopefully modestly priced - get a block of rooms w/ special rates
T-Shirt sales! Coffee mugs. Beer mugs.
Attendees - JW's and exJW's. The mental health community. Legal community.
Attendance? 500 feels closer to reality
Don't forget to have the big meetings taped and sell the tapes.