For a three-night trip with children, start with Holiday Inn Resort Vana Nava Hua Hin. Linked with the Vana Nava water park, it lets you spend a full day in the water worry-free thanks to December's clear, dry weather. Resorts like this often dress the grounds with trees and lights for the season, and the 27th-floor sky bar is an easy way to close out a family evening.
If a self-contained resort is the priority, compare Hyatt Regency Hua Hin and Movenpick Asara Resort & Spa Hua Hin. Hyatt has extensive grounds, several pools and The Barai Spa; Movenpick Asara is a low-rise 96-room garden resort with a free kids club and a yoga room, a good fit for a quiet Christmas.
For a balanced trip with both children and grandparents, Amari Hua Hin is worth a look: close to the central Hua Hin beachfront, it makes the night market and Market Village's year-end atmosphere easy to enjoy. If you want to trim the room bill and put water play first, AVANI+ Hua Hin (three pools with water slides) and Radisson Resort and Spa Hua Hin (private beach, free kids club) on the Cha-Am side are alternatives, both suited to a stay built around hotel facilities.
For a longer stay with several generations under one roof, consider Centara Grand Beach Resort & Villas Hua Hin and Anantara Hua Hin Resort & Spa. Villa-style rooms and generous gardens suit grandparents, adult children and grandchildren sharing space over Christmas, and both sit easily with a golfing member of the group.
Around December 25, Hua Hin sits in the most pleasant stretch of Thailand's dry season, so rain rarely disrupts plans - but it is also the year's highest-rate period, and Bangkok weekend traffic adds to the usual crowd. Before booking, check occupancy by room type, breakfast and transfer inclusions, the free-cancellation deadline and any peak minimum-stay rule in the current product details, and book early if your dates and room type are available.