Agree the constraints before the options: budget per person, maximum flight time, and the dates. Then shortlist three destinations that fit and hold a single vote. Groups stall because they debate destinations before they've agreed what's actually possible.
An open "where should we go?" invites answers across a $3,000 range and three continents, none of which can be compared. Fixing the budget and the flight-time ceiling first means every suggestion on the shortlist is a real option.
Someone will want something the group doesn't. Acknowledge it explicitly and give it a home — a day, a meal, a side trip — rather than letting it resurface as friction for the next four months.