What is the best way to book a Viking European cruise? Direct? CC program? Costco? My parents want to book a viking European small ship cruise for 2027 and business airfare.

What is the best way to book the cruise? Should I book direct with Viking? costco? Amex cruise program?

When do the typical summer peak dates sell out?...
https://www.flyertalk.com/foru....m/cruises/2205578-wh