Third wheel
Take a third person for free when you book a cabin for two on Star Clippers’ weeklong Tahiti cruise. Prices for trips May to December start at $2,125 for the first two passengers; a third guest pays only $220 in port taxes. Contact:

Steaming volcano
Get a fourth night free at Tabacón Grand Spa at the foot of Costa Rica’s Arenal volcano. Rates start at $1,135 and include a $100 spa credit and admission to hot springs and Temazcal sweat lodge. Through June 30. Contact:

Mouse bait
Book a four-night hotel and ticket package at Disney World, add another three nights’ hotel, and get three more days of tickets free. Seven days at the All-Star Movies Resort starts at $1,375 per person. Through June 27. Contact: