What's wrong with buying 16/17 1st class seats on the carrier of your choice, have some comfort, nice movie, no stops, bloody good meal, limo pickup, no hassle in immigration/customs if you pick the right carrier.
Unless you really need to spend at least twice as much on a charter for an aircraft big enough for the group, but quite uncomfortable for a long trip. Fantastic meals? Forget it. That's just my very rough guess of the cost. Don't forget you'll be paying for the dead leg as well, ie all the way back. In a previous existence I would have given you at least 40% off the published 1st class fare for a group that size, and carried you in the front instead of the usual freeloaders and staff.