Sam Roi Yot National Park anchors Hua Hin nature trips. Sam Roi Yod National Park (Private) tours the limestone hills, caves and coastal formations by private vehicle, running with little weather risk in December's dry season. Compare it against the shared format by group size and how much control over timing you need.
To look for wild elephants, Kuiburi National Park - Elephant watching (Join Tour) is the option. It observes wild animals, so sightings are not guaranteed, and departures are usually in the late afternoon. On a short trip, place it the day before Christmas Eve, and with children, set expectations about travel and waiting time in advance.
For a light look around town, Hua Hin City Tour (Private) is a solid default, leaving from the resort and covering the main points in a half day - useful for an awkward slot such as the morning after arrival. For an evening version, Hua hin by Night with Tuk Tuk (Private) is the alternative.
For a hands-on session, Takiab Thai cooking class in Hua Hin is largely indoors, so it works well as a family activity, and cooking something yourselves on a Christmas evening can add a nice personal touch. Check class duration, the menu, allergy handling and pickup terms in the product details.
To add activity, compare Tree Top Adventure Park Huahin and ATV Adventure Experience at Siam Milsim Hua Hin. Ziplines and off-road riding contrast sharply with resort downtime and add variety for a family with teenagers, but always confirm age, height or weight rules and safety equipment.
Before booking, confirm the meeting point and pickup, departure and return times, shared or private format, entrance fee and meal inclusions, minimum participants, age, height or weight rules, and cancellation or refund rules. Hua Hin has relatively few registered tour products, so availability can go quickly during the Christmas peak.