Short answer: The woodland below the moor is the sheltered option and it has four car parks. Parke, the National Trust estate on the edge of town, is the easiest walk from a car park in this area.
Yarner Wood, Parke and the moor — all free, all open. Bovey Tracey's position is the point: the woodland below the tors is sheltered when the high ground is not.
Ancient woodland in the East Dartmoor National Nature Reserve, with grassy glades, a river and a hide, and four car parks to choose from. Trees take a lot of weather out of a walk, and the going underfoot is far better than open moor in late December.
The National Trust estate on the edge of town — the easiest walk from a car park here, free for members, and it works in any weather.
Haytor and the open moor are a short drive up the road, if the weather is kind and you want the view.
Ring before you set off. Boxing Day hours are decided late, change year to year, and are the single thing most likely to be wrong online. A two-minute call beats a wasted drive.
Becky Falls and Canonteign Falls both close over Christmas, and several Dartmoor attractions reduce hours sharply from January. Ring rather than assume.
One Dartmoor warning that matters more on Boxing Day than any other day: the roads are unfenced with ponies and sheep standing on them, the weather turns fast, and the light goes by four. Start early and tell someone where you are going.
If you want to eat out, book now rather than in December. The places that do serve on Boxing Day fill weeks ahead, and the ones that do not take bookings have queues instead.
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