Below are my personal ideas how to avoid financial loss while travelling internationally on vacation/family trip:
1. Try to book most of the items online to reduce usage of cards upfront like flight, hotels, amusement park/zoo entry fees, shows, historical places, river cruise, cable car etc whenever possible. Just carry one card for offline payment to restaurant/shopping and enough local currencies. Set limit for per txn/day.
2. Have a secondary mobile to use for whatsapp, taking photos/videos. Keep the primary phone which is linked to banks either in locker/suitcase before stepping out of hotel.