Forget the locality. Best for your purposes is a large discount Cruise Only agency that has a GroupTravel Desk. I have used ones over years in Detroit area, New Hampshire and California .Vacationstogo.com has excellent website.Not always best deals though.Never booked a group but in past 1 free berth(bed), for every 8 bookings. You as originator would be entitled to these. The agent handles all details and monies, not you.All questions would be referred to them. So you need a really experienced,patient agent who knows how to handle all those first cruise questions.Onboard credits can be negotiated. Talk to a couple agencies.Pricing varies widely. Call cruise llines group desks directly also. Bon Voyage.